#include <bits/stdc++.h>
using namespace std;

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    //INT_MAX = 2147483647, UINT_MAX = 4294967295

    int s, w;
    cin >> s >> w;

    if(w >= s) cout << "unsafe\n";
    else cout << "safe\n";

    return 0;
}