#include<iostream>
using namespace std;
int main()
{
  int S,W;
  cin>>S>>W;
  if(S>!00||W>100||S<1||W<1)
  {
    cout<<"invalid input";
    system("pause");
  }
  if(W>=S)
  {
    cout<<"unsafe";
  }
  else
  {
    cout<<"safe";
  }
  return 0;
}
