import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int[] num = {1, 4, 8, 16, 32, 64, 128, 256, 512,  9, 27, 81, 243, 729,  16, 64, 256, 1024, 25, 125, 625,  36, 216,  49, 343,  64, 512,  81, 729,  100, 1000, 121,  144,  169,  196,  225,  256,  289,  324,  361,  400, 441, 484,  529,  576,  625,  676,  729,  784,  841, 900,  961};
        Arrays.sort(num);
        int X = sc.nextInt();
        int max = -1;
        for(int i = num.length; i > 0; i--){
            int n = num[i - 1];
            if(n <= X){
                max = Math.max(max, n);
                break;
            }
        }
        System.out.println(max);
    }
}

/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