#include <bits/stdc++.h>
using namespace std;

#define LL long long

#define FOR(INDEX, START, END) for (LL INDEX = (START); INDEX < (END); ++INDEX)
#define REP(INDEX, COUNT) for (LL INDEX = 0; INDEX < (COUNT); ++INDEX)

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

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

	return 0;
}
