// Vulnerability label: clean
pragma solidity ^0.4.24;
contract Ownable {
  address public owner;
  function Ownable() {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  function transferOwnership(address newOwner) onlyOwner {
    require(newOwner != address(0));      
    owner = newOwner;
  } 
}

contract Token is Ownable{
    uint256 public totalSupply;

    function balanceOf(address _owner) constant returns (uint256 balance);

    function transfer(address _to, uint256 _value) returns (bool success);

    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);

    function approve(address _spender, uint256 _value) returns (bool success);

    function allowance(address _owner, address _spender) constant returns (uint256 remaining);

    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

contract StandardToken is Token {
    function transfer(address _to, uint256 _value) returns (bool success) {
        require(balances[msg.sender] >= _value);
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        Transfer(msg.sender, _to, _value);
        return true;
    }


    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        require(balances[_from] >= _value && allowed[_from][msg.sender] >= _value);
        balances[_to] += _value;
        balances[_from] -= _value; 
        allowed[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value); 
        return true;
    }
    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }


    function approve(address _spender, uint256 _value) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
    
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
}

contract WanChainToken is StandardToken { 

    string public name;                   
    uint8 public decimals;               
    string public symbol; 
    uint256 public createTime;
    uint public releaseAmount = 350000000;
    mapping(uint => bool) public releaseMapping; 
     

    function WanChainToken() {
        balances[msg.sender] = 3000000000; 
        totalSupply = 10000000000;         
        name = "Wan Chain Token";                   
        decimals = 1;           
        symbol = "WLZJ";  
        createTime = now;
    }

    function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        require(_spender.call(bytes4(bytes32(sha3("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData));
        return true;
    }
    function release(uint month) onlyOwner{
        require(month >=1 && month <= 20 );
        require(now >= (month * 30 days) + createTime);
        require(!releaseMapping[month]);
        balances[owner] = balances[owner] + releaseAmount;
        releaseMapping[month] = true;
    }

}