#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define int long long
#define _GLIBCXX_DEBUG

signed main() {
  int N, M; cin >> N >> M;
  if(M>=N) cout << "unsafe" << endl;
  else cout << "safe" << endl;

}