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

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