#include <bits/stdc++.h>
#include <algorithm>
#define rep(i, n) for (int i=0; i<n; ++i)
#define all(obj) (obj).begin(),(obj).end()
using namespace std;
typedef long long ll;

int main(){
    int S, W;
    cin >> S >> W;
    if(S<=W) cout << "unsafe" << endl;
    else cout << "safe" << endl;
    return 0;

 }
