creation_sourcecode: pragma solidity ^0.7.1;
  // SPDX-License-Identifier: MIT
  /**
   * @title SafeMath
   * @dev Math operations with safety checks that revert on error
   */
  library SafeMath {
  
    /**
    * @dev Multiplies two numbers, 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 numbers truncating the quotient, reverts on division by zero.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
      require(b > 0); // Solidity only automatically asserts when dividing by 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 numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
      require(b <= a);
      uint256 c = a - b;
  
      return c;
    }
  
    /**
    * @dev Adds two numbers, 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 numbers 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;
    }
  }
  
  /**
   * @title ERC20 interface
   * @dev see https://github.com/ethereum/EIPs/issues/20
   */
   interface IERC20 {
     function totalSupply() external view returns (uint256);
  
     function balanceOf(address who) external view returns (uint256);
  
     function allowance(address owner, address spender)
       external view returns (uint256);
  
     function transfer(address to, uint256 value) external returns (bool);
  
     function approve(address spender, uint256 value)
       external returns (bool);
  
     function transferFrom(address from, address to, uint256 value)
       external returns (bool);
  
     event Transfer(
       address indexed from,
       address indexed to,
       uint256 value
     );
  
     event Approval(
       address indexed owner,
       address indexed spender,
       uint256 value
     );
   }
  
  contract ERC20 is IERC20 {
    using SafeMath for uint256;
  
    mapping (address => uint256) private _balances;
  
    mapping (address => mapping (address => uint256)) private _allowed;
  
    uint256 private _totalSupply;
    string private _name;
    string private _symbol;
    uint8 private _decimals;
  
    constructor(string memory name, string memory symbol, uint8  decimals, uint256  totalSupply) {
      _name = name;
      _symbol = symbol;
      _decimals = decimals;
      _totalSupply = totalSupply;
      _balances[msg.sender] = _balances[msg.sender].add(_totalSupply);
      emit Transfer(address(0), msg.sender, totalSupply);
    }
  
    /**
     * @return the name of the token.
     */
    function name() public view returns(string memory) {
      return _name;
    }
  
    /**
     * @return the symbol of the token.
     */
    function symbol() public view returns(string memory) {
      return _symbol;
    }
  
    /**
     * @return the number of decimals of the token.
     */
    function decimals() public view returns(uint8) {
      return _decimals;
    }
  
    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view override(IERC20) returns (uint256) {
      return _totalSupply;
    }
  
    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view override(IERC20) 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
      override(IERC20)
      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 override(IERC20) returns (bool) {
      _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 override(IERC20) returns (bool) {
      require(spender != address(0));
  
      _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
      override(IERC20)
      returns (bool)
    {
      require(value <= _allowed[from][msg.sender]);
  
      _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
      _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 increaseAllowance(
      address spender,
      uint256 addedValue
    )
      public
      returns (bool)
    {
      require(spender != address(0));
  
      _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 decreaseAllowance(
      address spender,
      uint256 subtractedValue
    )
      public
      returns (bool)
    {
      require(spender != address(0));
  
      _allowed[msg.sender][spender] = (
        _allowed[msg.sender][spender].sub(subtractedValue));
      emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
      return true;
    }
  
    /**
    * @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, uint256 value) internal {
      require(value <= _balances[from]);
      require(to != address(0));
  
      _balances[from] = _balances[from].sub(value);
      _balances[to] = _balances[to].add(value);
      emit Transfer(from, to, value);
    }
  }