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

int main() 
{
    int s, w;
    cin >> s >> w;

    if (w>= s) cout << "unsafe" << endl;
    else cout << "safe" << endl;
    return 0;
}
