import java.util.*;
class Main
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        int x = scan.nextInt();
        int num = 1;

        for(int i = 2; i <= 31; i++)
        {
            for(int j = 10; j > 1; j--)
            {
                double tmp = Math.pow(i, j);
                if(tmp <= x && tmp > num) num = (int) tmp;
            }
        }
        System.out.print(num);
        scan.close();
    }
}
/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