#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
typedef int64_t Int;

int main(){
    int S, W;
    cin >> S >> W;

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