#include<iostream> 
using namespace std;
int main(){
   int n;
   cin >> n;
   for (int i = n;i > 1;i--)
   {
      if (n % i == 0)
      {
         int flag = 1;
         for (int j = 2;j < i;j++)
         {
            if (i % j == 0)
            {
               flag = 0;
               break;
            }
         }
         if (flag == 1)
         {
            cout << i;
            break;
         }

      }
   }
   return 0;
}