import java.util.*;
class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
         int x = Integer.parseInt(sc.next());
         int ans = 1;
         for(int i =2;i<=x;i++){
             for(int j = i*i;j<=x;j=j*i){
                 ans = Math.max(ans,j);
             }
         }
         System.out.println(ans);
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz