#include <bits/stdc++.h>
using namespace std;
 
#define rep(i,n) for (int i = 0; i<(n); i++)
#define in(n) cin >> (n)
#define out(ans) cout << (ans) << endl;
using ll = int64_t;
using v = vector<int>;

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