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

int main() {
  ll s,w=0;

  cin >> s >> w;

  if (s<=w) cout << "unsafe" << endl;
  else  cout << "safe" << endl;
  return 0;
}