contract StandardToken is Token, SafeMath {
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
    uint256 public totalSupply;

    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);

        emit Transfer(msg.sender, to, tokens);

        return true;
    }

    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);

        emit Transfer(from, to, tokens);

        return true;
    }

    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }

    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;

        emit Approval(msg.sender, spender, tokens);

        return true;
    }

    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }


    function burn(uint256 _value) public returns (bool success) {
        require(balances[msg.sender] >= _value);                         // Check if the sender has enough
        balances[msg.sender] = safeSub(balances[msg.sender], _value);    // Subtract from the sender
        totalSupply = safeSub(totalSupply,_value);                       // Updates totalSupply

        emit Burn(msg.sender, _value);

        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balances[_from] >= _value);                                        // Check if the targeted balance is enough
        require(_value <= allowed[_from][msg.sender]);                             // Check allowance
        balances[_from] = safeSub(balances[_from],_value);                         // Subtract from the targeted balance
        allowed[_from][msg.sender] = safeSub(allowed[_from][msg.sender],_value);   // Subtract from the sender's allowance
        totalSupply = safeSub(totalSupply,_value);                                 // Update totalSupply
        emit    Burn(_from, _value);
        return true;
    }
}
function burnFrom(address _from, uint256 _value) public returns (bool success) {
    require(balances[_from] >= _value);                                        // Check if the targeted balance is enough
    require(_value <= allowed[_from][msg.sender]);                             // Check allowance
    balances[_from] = safeSub(balances[_from],_value);                         // Subtract from the targeted balance
    allowed[_from][msg.sender] = safeSub(allowed[_from][msg.sender],_value);   // Subtract from the sender's allowance
    totalSupply = safeSub(totalSupply,_value);                                 // Update totalSupply
    emit    Burn(_from, _value);
    return true;
}

/**
 * Destroy tokens from other account
 *
 * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
 *
 * @param _from the address of the sender
 * @param _value the amount of money to burn
 */