#include <bits/stdc++.h>

using namespace std;
const double PI=3.14159265358979323846;

#define SIZE_OF_ARRAY(array) (sizeof(array)/sizeof(array[0]))


int main() {

	int S, W;

	cin >> S >> W;

	string ans = "safe";
	if (S <= W) ans = "unsafe";
	
	cout << ans << endl;
}