import java.util.*;

public class Main {

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int max = 1;
		for (int i = 2; i <= 100; i++) {
			for (int j = 2; j < 10; j++) {
				int target = (int)Math.pow(i, j);
				if (target > x) {
					break;
				}
				if (target > max) {
					max = target;
				}
			}
		}
		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