#define _USE_MATH_DEFINES
#include<bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < (int)n; i++)
#define ll long long
#define MAX 10000000
#define SENTINEL 2e10;


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