#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() {
  int s,w;
  cin >> s >> w;
  if(s<=w)
    cout << 'unsafe' << endl;
  else
    cout << 'safe' << endl;
  return 0;
}