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

#pragma GCC optimize "O3"
#define rep(i,a,n) for(int i=a; i<n; i++)
typedef long long ll;
typedef pair<int,int> P;
const ll MOD = (int)1e9+7;
const ll INF = MOD*MOD;
const ll powll = 1LL<<1;

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