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

int main() {
	int S, W;
	cin >> S >> W;

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

	return 0;
}