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

template <class _T> inline bool chmax (_T& a,_T b){if(a<b){a=b;return true;}return false;}
template <class _T> inline bool chmin (_T& a,_T b){if(a>b){a=b;return true;}return false;}

const long long INF = 1LL << 60;
const long long mod = 1000000007;


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