contract PausableToken is ERC20Basic, Pausable {
    using SafeMath for uint256;

    mapping(address => uint256) internal balances;
    mapping (address => mapping (address => uint256)) internal allowed;

    uint256  internal totalSupply_;

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

    /**
    * @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 override virtual returns (bool) {
        require(_to != address(0), "trasferring to zero address");
        require(_value <= balances[msg.sender], "transfer amount exceeds available balance");
        require(!paused, "token transfer while paused");
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
    * @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 override view returns (uint256) {
        return balances[_owner];
    }

    /**
    * @dev Transfer tokens from one address to another based on allowance
    * @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 override virtual returns (bool) {
        require(_from != address(0), "from must not be zero address"); 
        require(_to != address(0), "to must not be zero address"); 
        require(!paused, "token transfer while paused");
        require(_value <= allowed[_from][msg.sender], "tranfer amount exceeds allowance");
        require(_value <= balances[_from], "transfer amount exceeds available balance");
        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 Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * Because approve/tranferFrom method is susceptible of multiple withdrawal attack,
    * please be careful when using approve additional amount of tokens.
    * Before approving additional allowances to a certain address, 
    * it is desired to check the changes of allowance of the address due to previous transferFrom activities.
    * @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 override returns (bool) {
        require(_spender != address(0), "approving to a zero address");
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
    * @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 override view returns (uint256) {
        return allowed[_owner][_spender];
    }

    /**
    * @dev Increase the amount of tokens that an owner allowed to a spender.
    * @param _spender The address which will spend the funds.
    * @param _addedValue The amount of tokens to increase the allowance by.
    */
    function increaseApproval(
        address _spender,
        uint _addedValue
    )
        public 
        returns (bool)
    {
        require(_spender != address(0), "approving to zero address");
        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.
    * @param _spender The address which will spend the funds.
    * @param _subtractedValue The amount of tokens to decrease the allowance by.
    */
    function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool)
    {
        require(_spender != address(0), "spender must not be a zero address");
        uint 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;
    }

}
/**
 * @title ERC20 Pausable token
 */
function balanceOf(address _owner) public override view returns (uint256) {
    return balances[_owner];
}

/**
 * @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.
 */