contract StandardToken is ERC20, Pausable {
    using SafeMath for uint256;

    mapping(address => uint256) private balances_;

    mapping(address => mapping(address => uint256)) private allowed_;

    uint256 private totalSupply_;

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public view returns (uint256) {
        return balances_[_owner];
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(
        address _owner,
        address _spender
    )
    public
    view
    returns (uint256)
    {
        return allowed_[_owner][_spender];
    }

    /**
    * @dev Transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
        require(_value <= balances_[msg.sender]);
        require(_to != address(0));

        balances_[msg.sender] = balances_[msg.sender].sub(_value);
        balances_[_to] = balances_[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
        allowed_[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns (bool)
    {
        require(_value <= balances_[_from]);
        require(_value <= allowed_[_from][msg.sender]);
        require(_to != address(0));

        balances_[_from] = balances_[_from].sub(_value);
        balances_[_to] = balances_[_to].add(_value);
        allowed_[_from][msg.sender] = allowed_[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * @param _spender The address which will spend the funds.
     * @param _addedValue The amount of tokens to increase the allowance by.
     */
    function increaseApproval(
        address _spender,
        uint256 _addedValue
    )
    public
    whenNotPaused
    returns (bool)
    {
        allowed_[msg.sender][_spender] = (
        allowed_[msg.sender][_spender].add(_addedValue));
        emit Approval(msg.sender, _spender, allowed_[msg.sender][_spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * @param _spender The address which will spend the funds.
     * @param _subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseApproval(
        address _spender,
        uint256 _subtractedValue
    )
    public
    whenNotPaused
    returns (bool)
    {
        uint256 oldValue = allowed_[msg.sender][_spender];
        if (_subtractedValue >= oldValue) {
            allowed_[msg.sender][_spender] = 0;
        } else {
            allowed_[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed_[msg.sender][_spender]);
        return true;
    }

    /**
     * @dev Internal function that mints an amount of the token and assigns it to
     * an account. This encapsulates the modification of balances such that the
     * proper events are emitted.
     * @param _account The account that will receive the created tokens.
     * @param _amount The amount that will be created.
     */
    function _mint(address _account, uint256 _amount) internal {
        require(_account != 0);
        totalSupply_ = totalSupply_.add(_amount);
        balances_[_account] = balances_[_account].add(_amount);
        emit Transfer(address(0), _account, _amount);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account.
     * @param _account The account whose tokens will be burnt.
     * @param _amount The amount that will be burnt.
     */
    function _burn(address _account, uint256 _amount) internal {
        require(_account != 0);
        require(_amount <= balances_[_account]);

        totalSupply_ = totalSupply_.sub(_amount);
        balances_[_account] = balances_[_account].sub(_amount);
        emit Transfer(_account, address(0), _amount);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account, deducting from the sender's allowance for said account. Uses the
     * internal _burn function.
     * @param _account The account whose tokens will be burnt.
     * @param _amount The amount that will be burnt.
     */
    function _burnFrom(address _account, uint256 _amount) internal {
        require(_amount <= allowed_[_account][msg.sender]);

        // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
        // this function needs to emit an event with the updated approval.
        allowed_[_account][msg.sender] = allowed_[_account][msg.sender].sub(
            _amount);
        _burn(_account, _amount);
    }
}
/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
 * Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
function _burn(address _account, uint256 _amount) internal {
        require(_account != 0);
        require(_amount <= balances_[_account]);

        totalSupply_ = totalSupply_.sub(_amount);
        balances_[_account] = balances_[_account].sub(_amount);
        emit Transfer(_account, address(0), _amount);
    }
/**
 * @dev Internal function that burns an amount of the token of a given
 * account.
 * @param _account The account whose tokens will be burnt.
 * @param _amount The amount that will be burnt.
 */