#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define REP(i,n) for(int i=0; i < n; i++)
#define ALL(n) begin(n), end(n)

int main()
{
  int s, w;

  cin >> s >> w;

  string ans;
  if(s <= w){
    ans = "unsafe";
  } else {
    ans = "safe";
  }

  cout << ans << endl;
}