using System;
//using System.Collections.Generic;

public class TestC
{
    public static void Main(){
        string line = Console.ReadLine();
        string[] numbers = line.Split(' ');
        int sheep = int.Parse(numbers[0]);
        int wolves = int.Parse(numbers[1]); 

        if(sheep <= wolves) Console.WriteLine("unsafe");
        else Console.WriteLine("safe");
    }
}