#include<stdio.h>
#include<iostream>
#include<math.h>
#include<string>
#include<vector>
#include<map>
#include<queue>
#include<cmath>
using namespace std;
using ll = long long int;
//typedef pair<int,int> P;
 
 int main(void){
	 int S,W;
	 cin >> S >> W;
	 if(S <= W){
		 cout << "unsafe" <<endl;
	 }else{
		 cout << "safe" <<endl;
	 }
 }