#include<bits/stdc++.h>

using namespace std;

typedef long long int ll;

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(0);cout.tie(0);

  ll s, w;
  cin >> s >> w;
  if(w >= s) cout << "unsafe" << endl;
  else cout << "safe" << endl;
}
