#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;

  bool res = w >= s;

  cout << (res ? "unsafe" : "safe") << endl;

  return 0;
}
