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

int main() {

int S,W;
cin >> S>>W ;

if(S<=W) cout << "unsafe" << endl;
else cout << "safe" << endl;



}