#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
int INF = 1000000009;
int main()
{
  int s,w;
  cin >> s >> w;
  if( w >= s){
    cout << "unsafe" << endl;
  }else{
    cout << "safe" << endl;
  }
}