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

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