#include<iostream>
using namespace std;
int main(){
  int S,W;
  cin>> S >> W;
  if(S<W){
    cout<< "unsafe" <<endl;
  }else if(S==W){
    cout<< "unsafe" <<endl;
  }else if(S>W){
    cout<< "safe" <<endl;
  }
  return 0;
}
