import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        try (Scanner in = new Scanner(System.in)) {
            int X = in.nextInt();

            boolean[] isBeki = new boolean[X + 1];
            isBeki[1] = true;
            bLoop: for (int b = 2; b < Math.sqrt(X) + 1; b++) {
                for (int n = b * b;; n *= b) {
                    if (n > X) {
                        continue bLoop;
                    }
                    isBeki[n] = true;
                }
            }

            for (int i = X; i >= 1; i--) {
                if (isBeki[i]) {
                    System.out.println(i);
                    return;
                }
            }
        }
    }
}

/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