import java.util.Scanner;

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

		int x = sc.nextInt();
		int ans = 1;

		for (int b = 1; b <= x; b++) {
			for (int p = 2; p < 1000; p++) {
				int pow = (int)Math.pow(b, p);
				if (pow <= x)
					if (ans < pow) ans = pow;
			}
		}
		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