#include <bits/stdc++.h>
#define ll long long int
#define MOD 1000000007
#define INF 1e18

using namespace std;

int main(void){
  ll s, w;
  cin >> s >> w;
  
  if (s <= w)
    cout << "unsafe" << endl;
  else
    cout << "safe" << endl;

  return 0;
}
