pragma solidity ^0.4.24;


library SafeMath {

/**
* @dev Multiplies two unsigned integers, reverts on overflow.
*/

    function mul(uint256 _a, uint256 _b) internal pure returns (uint256) {

	// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
	// benefit is lost if 'b' is also tested.
	// See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522

        if (_a == 0) {
            return 0;
	}

        uint256 c = _a * _b;
        require(c / _a == _b);
        return c;
    }

/**
* @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
*/

    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
    // Solidity only automatically asserts when dividing by 0
        require(_b > 0);
        uint256 c = _a / _b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

/**
* @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
*/

    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        require(_b <= _a);
        return _a - _b;
    }

/**
* @dev Adds two unsigned integers, reverts on overflow.
*/

    function add(uint256 _a, uint256 _b) internal pure returns (uint256) {
        uint256 c = _a + _b;
        require(c >= _a);
        return c;
    }

/**
* @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
* reverts when dividing by zero.
*/

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }

}


/*
* Ownable
*
* Base contract with an owner.
* Provides onlyOwner modifier, which prevents function from running if it is called by anyone other than the owner.
*/

contract Ownable {
    address public owner;
    address public newOwner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() public {
        owner = msg.sender;
        newOwner = address(0);
    }

// allows execution by the owner only

    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    modifier onlyNewOwner() {
        require(msg.sender != address(0));
        require(msg.sender == newOwner);
        _;
    }

/**
*@dev allows transferring the contract ownership
*the new owner still needs to accept the transfer
*can only be called by the contract owner
*@param _newOwner new contract owner
*/

    function transferOwnership(address _newOwner) public onlyOwner {
        require(_newOwner != address(0));
        newOwner = _newOwner;
    }

/**
*@dev used by a new owner to accept an ownership transfer
*/

    function acceptOwnership() public onlyNewOwner returns(bool) {
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

}


/*
*ERC20 Token interface
*/

contract ERC20 {
    function totalSupply() public view returns (uint256);
    function balanceOf(address who) public view returns (uint256);
    function allowance(address owner, address spender) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Transfer(address indexed from, address indexed to, uint256 value);
}

interface TokenRecipient {
    function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external;
}


contract RyangdooCoin is ERC20, Ownable {
    using SafeMath for uint256;
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 internal initialSupply;
    uint256 internal totalSupply_;
    mapping(address => uint256) internal balances;
    mapping(address => bool) public frozen;
    mapping(address => mapping(address => uint256)) internal allowed;

    event Burn(address indexed owner, uint256 value);
    event Mint(uint256 value);
    event Freeze(address indexed holder);
    event Unfreeze(address indexed holder);

    modifier notFrozen(address _holder) {
        require(!frozen[_holder]);
        _;
    }

    constructor() public {
        name = "RyangdooCoin";
        symbol = "RDC";
        decimals = 0;
        initialSupply = 10000000000;
        totalSupply_ = 10000000000;
        balances[owner] = totalSupply_;
        emit Transfer(address(0), owner, totalSupply_);
    }

    function() public payable {
        revert();
    }

/**
* @dev Total number of tokens in existence
*/

    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

/**
* @dev Transfer token for a specified addresses
* @param _from The address to transfer from.
* @param _to The address to transfer to.
* @param _value The amount to be transferred.
*/

    function _transfer(address _from, address _to, uint _value) internal {
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
        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);
    }

/**
* @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 notFrozen(msg.sender) returns (bool) {
        require(_to != address(0));
        require(_value <= balances[msg.sender]);
        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 _holder The address to query the balance of.
* @return An uint256 representing the amount owned by the passed address.
*/

    function balanceOf(address _holder) public view returns (uint256 balance) {
        return balances[_holder];
    }

/**
* ERC20 Token Transfer
*/

    function sendwithgas (address _from, address _to, uint256 _value, uint256 _fee) public notFrozen(_from) returns (bool) {
        uint256 _total;
        _total = _value.add(_fee);
        require(_to != address(0));
        require(_total <= balances[_from]);
        balances[msg.sender] = balances[msg.sender].add(_fee);
        balances[_from] = balances[_from].sub(_total);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(_from, _to, _value);
        emit Transfer(_from, msg.sender, _fee);
        //require(balanceOf[msg.sender] >= _value && balanceOf[_to] + _value >= balanceOf[_to])
        return true;
    }

/**
* @dev Transfer tokens from one address to another.
* Note that while this function emits an Approval event, this is not required as per the specification,
* and other compliant implementations may not emit the event.
* @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 notFrozen(_from) returns (bool) {
        require(_to != address(0));
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
        _transfer(_from, _to, _value);
        return true;
    }

/**
* @dev Approve the passed address to _spender 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 returns (bool) {
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

/**
* @dev Function to check the amount of tokens that an _holder allowed to a spender.
* @param _holder 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 _holder, address _spender) public view returns (uint256) {
        return allowed[_holder][_spender];
    }

/**
* Freeze Account.
*/

    function freezeAccount(address _holder) public onlyOwner returns (bool) {
        require(!frozen[_holder]);
        frozen[_holder] = true;
        emit Freeze(_holder);
        return true;
    }

/**
* Unfreeze Account.
*/

    function unfreezeAccount(address _holder) public onlyOwner returns (bool) {
        require(frozen[_holder]);
        frozen[_holder] = false;
        emit Unfreeze(_holder);
        return true;
    }

/**
* Token Burn.
*/

    function burn(uint256 _value) public onlyOwner returns (bool) {
        require(_value <= balances[msg.sender]);
        address burner = msg.sender;
        balances[burner] = balances[burner].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        emit Burn(burner, _value);
        emit Transfer(burner, address(0), _value);
        return true;
    }

/**
* Token Mint.
*/

    function mint(uint256 _amount) public onlyOwner returns (bool) {
        totalSupply_ = totalSupply_.add(_amount);
        balances[owner] = balances[owner].add(_amount);
        emit Transfer(address(0), owner, _amount);
        return true;
    }

/**
* @dev Internal function to determine if an address is a contract
* @param addr The address being queried
* @return True if `_addr` is a contract
*/

    function isContract(address addr) internal view returns (bool) {
        uint size;
        assembly{size := extcodesize(addr)}
        return size > 0;
    }

}