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

    int S, W;
    cin >> S >> W;

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

return 0;
}