public static void modulus(Stack<String> newStack) {
		if(!newStack.isEmpty() && newStack.size() >=2) {
			int firstNum = Integer.parseInt((String) newStack.peek());
			int secondNum = Integer.parseInt((String) newStack.peek());
			if(firstNum <=-1) {
				System.err.println("Negative power.");
			}
			else {
				firstNum = Integer.parseInt((String) newStack.pop());
				secondNum = Integer.parseInt((String) newStack.pop());
				newStack.push(userInput.saturation((long)(int)(secondNum%firstNum)));
			}
			}
		else {
			stackUnderflow();
		}
	}