contract ERC20Token {
    using SafeMath for uint;

    // ------------------------------------------------------------------------
    // Total Supply
    // ------------------------------------------------------------------------
    uint256 _totalSupply = 0;

    // ------------------------------------------------------------------------
    // Balances for each account
    // ------------------------------------------------------------------------
    mapping(address => uint256) balances;

    // ------------------------------------------------------------------------
    // Owner of account approves the transfer of an amount to another account
    // ------------------------------------------------------------------------
    mapping(address => mapping (address => uint256)) allowed;

    // ------------------------------------------------------------------------
    // Get the total token supply
    // ------------------------------------------------------------------------
    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }

    // ------------------------------------------------------------------------
    // Get the account balance of another account with address _owner
    // ------------------------------------------------------------------------
    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }

    // ------------------------------------------------------------------------
    // Transfer the balance from owner's account to another account
    // ------------------------------------------------------------------------
    function transfer(address _to, uint256 _amount) returns (bool success) {
        if (balances[msg.sender] >= _amount                // User has balance
            && _amount > 0                                 // Non-zero transfer
            && balances[_to] + _amount > balances[_to]     // Overflow check
        ) {
            balances[msg.sender] = balances[msg.sender].sub(_amount);
            balances[_to] = balances[_to].add(_amount);
            Transfer(msg.sender, _to, _amount);
            return true;
        } else {
            return false;
        }
    }

    // ------------------------------------------------------------------------
    // Allow _spender to withdraw from your account, multiple times, up to the
    // _value amount. If this function is called again it overwrites the
    // current allowance with _value.
    // ------------------------------------------------------------------------
    function approve(
        address _spender,
        uint256 _amount
    ) returns (bool success) {
        // Borrowed from the MiniMeToken contract
        // To change the approve amount you first have to reduce the addresses`
        //  allowance to zero by calling `approve(_spender,0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require((_amount == 0) || (allowed[msg.sender][_spender] == 0));

        allowed[msg.sender][_spender] = _amount;
        Approval(msg.sender, _spender, _amount);
        return true;
    }

    // ------------------------------------------------------------------------
    // Spender of tokens transfer an amount of tokens from the token owner's
    // balance to the spender's account. The owner of the tokens must already
    // have approve(...)-d this transfer
    // ------------------------------------------------------------------------
    function transferFrom(
        address _from,
        address _to,
        uint256 _amount
    ) returns (bool success) {
        if (balances[_from] >= _amount                  // From a/c has balance
            && allowed[_from][msg.sender] >= _amount    // Transfer approved
            && _amount > 0                              // Non-zero transfer
            && balances[_to] + _amount > balances[_to]  // Overflow check
        ) {
            balances[_from] = balances[_from].sub(_amount);
            allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_amount);
            balances[_to] = balances[_to].add(_amount);
            Transfer(_from, _to, _amount);
            return true;
        } else {
            return false;
        }
    }

    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(
        address _owner, 
        address _spender
    ) constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender,
        uint256 _value);
}
// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals
// https://github.com/ethereum/EIPs/issues/20
// ----------------------------------------------------------------------------
function totalSupply() constant returns (uint256 totalSupply) {
    totalSupply = _totalSupply;
}

// ------------------------------------------------------------------------
// Get the total token supply
// ------------------------------------------------------------------------