#include <iostream>
#include <bits/stdc++.h>
#include <vector>
#include <utility>
#include <string>
#include <math.h>
#include <algorithm>
#include <cstring>
#include <cctype>

typedef long long int lli;

using namespace std;

int main() {

   int S,W;
   cin >> S >> W;
   if(S<=W){
   cout << "unsafe" << endl;
   }else{
   cout << "safe" << endl;
   }
  
}