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

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