Contract Source Code:

pragma solidity ^0.5.9;
/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
	/**
	 * @dev Multiplies two numbers, throws on overflow.
	 */
	function mul(uint256 a, uint256 b) internal pure returns (uint256) {
		if (a == 0) {
		  return 0;
		}
		uint256 c = a * b;
		assert(c / a == b);
		return c;
	}
	/**
	 * @dev Integer division of two numbers, truncating the quotient.
	 */
	function div(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a / b;
		return c;
	}
	/**
	 * @dev Substracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
	 */
	function sub(uint256 a, uint256 b) internal pure returns (uint256) {
		assert(b <= a);
		return a - b;
	}
	/**
	 * @dev Adds two numbers, throws on overflow.
	 */
	function add(uint256 a, uint256 b) internal pure returns (uint256) {
		uint256 c = a + b;
		assert(c >= a);
		return c;
	}
}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 */
contract ERC20Basic {
	function totalSupply() public view returns (uint256);
	function balanceOf(address who) public view returns (uint256);
	function transfer(address to, uint256 value) public returns (bool);
	event Transfer(address indexed from, address indexed to, uint256 value);
}

/**
 * @title ERC20 interface
 */
contract ERC20 is ERC20Basic {
	function allowance(address owner, address spender) public view returns (uint256);
	function transferFrom(address from, address to, uint256 value) public returns (bool);
	function approve(address spender, uint256 value) public returns (bool);
	event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract Ownable {
	address public owner;
	event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
	
	/**
	 * @dev The Ownable constructor sets the original `owner` of the contract to the sender
	 * account.
	 */
	constructor() public {
		owner = msg.sender;
	}
	/**
	 * @dev Throws if called by any account other than the owner.
	 */
	modifier onlyOwner() {
		require(msg.sender == owner);
		_;
	}

	/**
	 * @dev Allows the current owner to transfer control of the contract to a newOwner.
	 * @param newOwner The address to transfer ownership to.
	 */
	function transferOwnership(address newOwner) public onlyOwner {
		require(newOwner != address(0));
		emit OwnershipTransferred(owner, newOwner);
		owner = newOwner;
	}
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic,ERC20 {
	using SafeMath for uint256;
	mapping(address => uint256) balances;
	mapping(address => uint256) public lockValues; //lock the amount of the specified address.
	uint256 totalSupply_ = 1000000000*10**8; //total
	/**
	 * @dev total number of tokens in existence
	 */
	function totalSupply() public view returns (uint256) {
		return totalSupply_;
	}
	/**
	 * @dev transfer token for a specified address
	 * @param _to The address to transfer to.
	 * @param _value The amount to be transferred.
	 */
	function transfer(address _to, uint256 _value) public returns (bool) {
		require(_to != address(0));
		address addr = msg.sender;
		require(_value <= balances[addr]);
		uint256 transBlalance = balances[msg.sender].sub(lockValues[msg.sender]);
		require(_value <= transBlalance);
		// SafeMath.sub will throw if there is not enough balance.
		balances[msg.sender] = balances[msg.sender].sub(_value);
		balances[_to] = balances[_to].add(_value);
		emit Transfer(msg.sender, _to, _value);
		return true;
	}
	/**
	 * @dev Gets the balance of the specified address.
	 * @param _owner The address to query the the balance of.
	 * @return An uint256 representing the amount owned by the passed address.
	 */
	function balanceOf(address _owner) public view returns (uint256 balance) {
		return balances[_owner];
	}
}

/**
 * @title Standard ERC20 token
 * @dev Implementation of the basic standard token.
 */
contract StandardToken is ERC20, BasicToken {
	mapping (address => mapping (address => uint256)) internal allowed;
	/**
	 * @dev Transfer tokens from one address to another
	 * @param _from address The address which you want to send tokens from
	 * @param _to address The address which you want to transfer to
	 * @param _value uint256 the amount of tokens to be transferred
	 */
	function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
		require(_to != address(0));
		require(_value <= balances[_from]);
		require(_value <= allowed[_from][msg.sender]);
		uint256 transBlalance = balances[_from].sub(lockValues[_from]);
		require(_value <= transBlalance);
		transBlalance = allowed[_from][msg.sender].sub(lockValues[msg.sender]);
		require(_value <= transBlalance);
		balances[_from] = balances[_from].sub(_value);
		balances[_to] = balances[_to].add(_value);
		allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
		emit Transfer(_from, _to, _value);
		return true;
	}

	/**
	 * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
	 *
	 * Beware that changing an allowance with this method brings the risk that someone may use both the old
	 * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
	 * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
	 * @param _spender The address which will spend the funds.
	 * @param _value The amount of tokens to be spent.
	 */
	function approve(address _spender, uint256 _value) public returns (bool) {
		allowed[msg.sender][_spender] = _value;
		emit Approval(msg.sender, _spender, _value);
		return true;
	}
	/**
	 * @dev Function to check the amount of tokens that an owner allowed to a spender.
	 * @param _owner address The address which owns the funds.
	 * @param _spender address The address which will spend the funds.
	 * @return A uint256 specifying the amount of tokens still available for the spender.
	 */
	function allowance(address _owner, address _spender) public view returns (uint256) {
		return allowed[_owner][_spender];
	}
	/**
	 * @dev Increase the amount of tokens that an owner allowed to a spender.
	 *
	 * approve should be called when allowed[_spender] == 0. To increment
	 * allowed value is better to use this function to avoid 2 calls (and wait until
	 * the first transaction is mined)
	 * From MonolithDAO Token.sol
	 * @param _spender The address which will spend the funds.
	 * @param _addedValue The amount of tokens to increase the allowance by.
	 */
	function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
		allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
		emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}

	/**
	 * @dev Decrease the amount of tokens that an owner allowed to a spender.
	 *
	 * approve should be called when allowed[_spender] == 0. To decrement
	 * allowed value is better to use this function to avoid 2 calls (and wait until
	 * the first transaction is mined)
	 * From MonolithDAO Token.sol
	 * @param _spender The address which will spend the funds.
	 * @param _subtractedValue The amount of tokens to decrease the allowance by.
	 */
	function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
		uint oldValue = allowed[msg.sender][_spender];
		if (_subtractedValue > oldValue) {
		  allowed[msg.sender][_spender] = 0;
		} else {
		  allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
		}
		emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
		return true;
	}
}

/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
	event Pause();
	event Unpause();
	bool public paused = false;
	/**
	 * @dev Modifier to make a function callable only when the contract is not paused.
	 */
	modifier whenNotPaused() {
		require(!paused);
		_;
	}
	/**
	 * @dev Modifier to make a function callable only when the contract is paused.
	 */
	modifier whenPaused() {
		require(paused);
		_;
	}
	/**
	 * @dev called by the owner to pause, triggers stopped state
	 */
	function pause() onlyOwner whenNotPaused public {
		paused = true;
		emit Pause();
	}
	/**
	 * @dev called by the owner to unpause, returns to normal state
	 */
	function unpause() onlyOwner whenPaused public {
		paused = false;
		emit Unpause();
	}
}
/**
 * @title Pausable token
 * @dev StandardToken modified with pausable transfers.
 **/
contract PausableToken is StandardToken, Pausable {
	function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
		return super.transfer(_to, _value);
	}

	function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) {
		return super.transferFrom(_from, _to, _value);
	}
	function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
		return super.approve(_spender, _value);
	}
	function increaseApproval(address _spender, uint _addedValue) public whenNotPaused returns (bool success) {
		return super.increaseApproval(_spender, _addedValue);
	}
	function decreaseApproval(address _spender, uint _subtractedValue) public whenNotPaused returns (bool success) {
		return super.decreaseApproval(_spender, _subtractedValue);
	}
}

/**
 * @dev Token ERC20 contract
 */
contract ATokenERC20 is PausableToken {
	string public constant version = "1.0";
	string public name = "Step chain";
	string public symbol = "IOC";
	uint8 public constant decimals = 8;
	
	constructor() public {
		balances[msg.sender] = totalSupply_;
	}

	function addLockValue(address addr,uint256 _value) public onlyOwner {
		uint256 _reqlockValues= lockValues[addr].add(_value);
		require(_reqlockValues <= balances[addr]);    
		require(addr != address(0));
		lockValues[addr] = lockValues[addr].add(_value);        
	}    
	function subLockValue(address addr,uint256 _value) public onlyOwner {
		require(addr != address(0));
		require(_value <= lockValues[addr]);
		lockValues[addr] = lockValues[addr].sub(_value);        
	}
}