import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		sc.close();
		int max = 0;
		for (int i = 1; i <= 1000; ++i) {
			if (i != 1) {
				for (int j = 2; j <= 10; ++j) {
					int tmp = (int) Math.pow(i, j);
					if (tmp <= x)
						max = Math.max(max, tmp);
					else
						break;
				}
			} else {
				if (i <= x)
					max = Math.max(max, i);
			}
		}
		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