/**
 *Submitted for verification at Etherscan.io on 2021-02-09
*/

pragma solidity ^0.5.0;

library SafeMath {
    
function mul(uint256 _a, uint256 _b) internal pure returns (uint256) {
    if (_a == 0) {
        return 0;
    }
    
    uint256 c = _a * _b;
    require(c / _a == _b);
    return c;
}

function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
    require(_b > 0);
    uint256 c = _a / _b;
    return c;
}

function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
    require(_b <= _a);
    return _a - _b;
}

function add(uint256 _a, uint256 _b) internal pure returns (uint256) {
    uint256 c = _a + _b;
    require(c >= _a);
    return c;
}

function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0);
    return a % b;
    
    }
}

contract Ownable {
    address public owner;
    address public newOwner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    
constructor() public {
    owner = msg.sender;
    newOwner = address(0);
}

modifier onlyOwner() {
    require(msg.sender == owner);
    _;
}

modifier onlyNewOwner() {
    require(msg.sender != address(0));
    require(msg.sender == newOwner);
    _;
}

function transferOwnership(address _newOwner) public onlyOwner {
    require(_newOwner != address(0));
    newOwner = _newOwner;
}

function acceptOwnership() public onlyNewOwner {
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
}
}

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 calldata) external;

}

contract QVING 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 Freeze(address indexed holder);
    event Unfreeze(address indexed holder);
    
    modifier notFrozen(address _holder) {
        require(!frozen[_holder]);
        _;
    }
    
constructor() public {
    name = "Qving";
    symbol = "QVI";
    decimals = 18;
    initialSupply = 500000000;
    totalSupply_ = initialSupply * 10 ** uint(decimals);
    balances[owner] = totalSupply_;
    emit Transfer(address(0), owner, totalSupply_);
}

function() external payable {
    revert();
}

function totalSupply() public view returns (uint256) {
    return totalSupply_;
}

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);
}

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;
}

function balanceOf(address _holder) public view returns (uint256 balance) {
    return balances[_holder];
}

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;
}

function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
}

function allowance(address _holder, address _spender) public view returns (uint256) {
    return allowed[_holder][_spender];
}

function freezeAccount(address _holder) public onlyOwner returns (bool) {
    require(!frozen[_holder]);
    frozen[_holder] = true;
    emit Freeze(_holder);
    return true;
}

function unfreezeAccount(address _holder) public onlyOwner returns (bool) {
    require(frozen[_holder]);
    frozen[_holder] = false;
    emit Unfreeze(_holder);
    return true;
}

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);
    
    return true;
}

function isContract(address addr) internal view returns (bool) {
    uint size;
    assembly{size := extcodesize(addr)}
    return size > 0;
}
}

{
  "compilationTarget": {
    "QVING.sol": "QVING"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}