  function withdraw(uint amount) public {
    require(!safeGuard,"System Paused by Admin");
    require(tokens[address(0)][msg.sender] >= amount);
    tokens[address(0)][msg.sender] = tokens[address(0)][msg.sender].sub(amount);
    msg.sender.transfer(amount);
    emit Withdraw(now, address(0), msg.sender, amount, tokens[address(0)][msg.sender]);
  }