#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()
typedef long long lint;
 
int main() {
  int s,w;
  cin >> s >> w;
  
  if(w>=s)cout << "unsafe" << endl;
  else cout << "safe" << endl;
}

