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• library MerkleProof
•    - function verify(bytes32[] memory proo ...
• interface I_ERC20
•    - function transfer(address recipient, ...
• interface I_MerkleDistributor
•    - function token()
•    - function merkleRoot()
•    - function isClaimed(uint256 index)
•    - function claim(uint256 index, address ...
•  contract MerkleDistributor is I_Me ... *
•    - function isClaimed(uint256 index)
•    - function _setClaimed(uint256 index)
•    - function claim(uint256 index, address ...

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/**
 *Submitted for verification at Etherscan.io on 2021-02-15
*/

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.6.0;

/// @dev These functions deal with verification of Merkle trees (hash trees),
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        bytes32 computedHash = leaf;

        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];

            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }

        // Check if the computed hash (root) is equal to the provided root
        return computedHash == root;
    }
}

/// @dev Interface of the ERC20 standard with only the funcions we need
interface I_ERC20 {
    function transfer(address recipient, uint256 amount) external returns (bool);
}

/// @dev Allows anyone to claim a token if they exist in a merkle root.
interface I_MerkleDistributor {

    /// @dev Returns the address of the token distributed by this contract.
    function token() external view returns (address);

    /// @dev Returns the merkle root of the merkle tree containing account balances available to claim.
    function merkleRoot() external view returns (bytes32);

    /// @dev Returns true if the index has been marked claimed.
    function isClaimed(uint256 index) external view returns (bool);

    /// @dev Claim the given amount of the token to the given address. Reverts if the inputs are invalid.
    function claim(uint256 index, address account, uint256 amount, bytes32[] calldata merkleProof) external;

    /// @dev This event is triggered whenever a call to #claim succeeds.
    event Claimed(uint256 index, address account, uint256 amount);
}

contract MerkleDistributor is I_MerkleDistributor {
    address public immutable override token;
    bytes32 public immutable override merkleRoot;

    // This is a packed array of booleans.
    mapping(uint256 => uint256) private claimedBitMap;

    constructor(address _token, bytes32 _merkleRoot) public {
        token = _token;
        merkleRoot = _merkleRoot;
    }

    function isClaimed(uint256 index) public view override returns (bool) {
        uint256 claimedWordIndex = index / 256;
        uint256 claimedBitIndex = index % 256;
        uint256 claimedWord = claimedBitMap[claimedWordIndex];
        uint256 mask = (1 << claimedBitIndex);
        return claimedWord & mask == mask;
    }

    function _setClaimed(uint256 index) private {
        uint256 claimedWordIndex = index / 256;
        uint256 claimedBitIndex = index % 256;
        claimedBitMap[claimedWordIndex] = claimedBitMap[claimedWordIndex] | (1 << claimedBitIndex);
    }

    function claim(uint256 index, address account, uint256 amount, bytes32[] calldata merkleProof) external override {
        require(msg.sender == account, 'claim: Only account may withdraw'); // self-request only
        require(!isClaimed(index), 'MerkleDistributor: Drop already claimed.');

        // Verify the merkle proof.
        bytes32 node = keccak256(abi.encodePacked(index, account, amount));
        require(MerkleProof.verify(merkleProof, merkleRoot, node), 'MerkleDistributor: Invalid proof.');

        require(I_ERC20(token).transfer(account, amount), 'MerkleDistributor: Transfer failed.');

        // Mark it claimed and send the token.
        _setClaimed(index);
        
        emit Claimed(index, account, amount);
    }
}

• No Contract Security Audit Submitted- Submit Audit Here

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000000000000000000000000f157b7ba35089c9b0f02c24bbe1e03855dbe5c1f2490acba7a30fda9317f6f7f837f39d52d6624ff189a9a24094ada49527ecc89

-----Decoded View---------------
Arg [0] : _token (address): 0xF157b7Ba35089c9b0F02C24BBE1E03855dBE5c1F
Arg [1] : _merkleRoot (bytes32): 0x2490acba7a30fda9317f6f7f837f39d52d6624ff189a9a24094ada49527ecc89

-----Encoded View---------------
2 Constructor Arguments found :
Arg [0] : 000000000000000000000000f157b7ba35089c9b0f02c24bbe1e03855dbe5c1f
Arg [1] : 2490acba7a30fda9317f6f7f837f39d52d6624ff189a9a24094ada49527ecc89

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ipfs://cce9202b1982dc1e5be36a5bab9b713cd4d33605509198e61f34b0f123f3d233