#include <iostream>
#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
#define rep(i,n) for(int i = 0; i < ((int)(n)); i++)   // 0-indexed昇順

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