pragma solidity ^0.4.16;

contract Token{
    uint256 public totalSupply;

    function balanceOf(address _owner) public view returns (uint256 balance);
    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns
    (bool success);

    function approve(address _spender, uint256 _value) public returns (bool success);

    function allowance(address _owner, address _spender) public view returns
    (uint256 remaining);

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256
    _value);
}

contract TokenERC20 is Token {

    string public name;
    uint8 public decimals;
    string public symbol;

    constructor(uint256 _initialAmount, string _tokenName, uint8 _decimalUnits, string _tokenSymbol) public {
        totalSupply = _initialAmount * 10 ** uint256(_decimalUnits);
        balances[msg.sender] = totalSupply;

        name = _tokenName;
        decimals = _decimalUnits;
        symbol = _tokenSymbol;
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(balances[msg.sender] >= _value && balances[_to] + _value > balances[_to]);
        require(_to != 0x0);
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        emit Transfer(msg.sender, _to, _value);
        return true;
    }


    function transferFrom(address _from, address _to, uint256 _value) public returns
    (bool success) {
        require(balances[_from] >= _value && allowed[_from][msg.sender] >= _value);
        balances[_to] += _value;
        balances[_from] -= _value;
        allowed[_from][msg.sender] -= _value;
        emit Transfer(_from, _to, _value);
        return true;
    }
    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }


    function approve(address _spender, uint256 _value) public returns (bool success)
    {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
}