import java.util.*;

public class Main {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		if(x <= 3) {
			System.out.println(1);
			return;
		}
		outside: for(int i = x; ; i--) {
			for(int j = 2; j * j <= i; j++) {
				for(int k = 2; Math.pow(j, k) <= i; k++) {
					if(Math.pow(j, k) == i) {
						System.out.println(i);
						break outside;
					}
				}
			}
		}
	}
}
/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