import java.util.Scanner;

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

		if(x == 1) {
			System.out.println(1);
			return;
		}

		int ans = 0;
		for (int b = 2; b <= 1000; b++) {
			int p = 2;
			while(Math.pow(b, p) <= x) {
				int num = (int)Math.pow(b, p);
				p++;
				ans = Math.max(ans, num);
			}
		}

		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