#include<bits/stdc++.h>
#define rep(i,N) for(ll (i)=0;(i)<(N);(i)++)
#define chmax(x,y) x=max(x,y)
#define chmin(x,y) x=min(x,y)
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
const int mod = 1000000007;

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