//----------------------------------------------------------------------
#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)   FOR(i,0,n)
//----------------------------------------------------------------------

using namespace std;
using ll = long long;
using P = pair<int,int>;
using Graph = vector<vector<int>>;

int main(void) {
    int s, w;
    cin >> s >> w;
    cout << (w >= s ? "unsafe" : "safe") << endl;
    return 0;
}