#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
#define yorn(f) puts((f)?"safe":"unsafe")
#define YORN(f) puts((f)?"YES":"NO")
ll s,w;
//ld ;
//string s;
// char c;

int main() {
  cin >> s >> w;
  yorn(s>w);
  return 0;
}