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

int main() {
    int s,w;
    cin >> s >> w;
    if(w >= s){
        cout << "unsafe" << endl;
    }else{
        cout << "safe" << endl;
    }
    return 0;
}