#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
using P = pair <int, int>;


int main() {
int s,w ;
cin >> s>>w;
if (w>=s) cout <<"unsafe" << endl;
else cout<< "safe" <<endl;
}