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

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

}

int main(){
    long long S;
    scanf("%lld",&S);
    long long W;
    scanf("%lld",&W);
    solve(S, W);
    return 0;
}
