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

int main(){
  string ans = "safe"
  cin >> s >> w;
  if (s<=w){
    ans = "unsafe";
  }
  cout << ans << endl;
}