#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define INF 1000000000000 //10^12

int main(){

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