import java.util.Scanner;
public class Main {
 
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		int tmp=1;
		for(int i=1;i<X;i++) {
			for(int j=2;j<=100;j++) {
				if(Math.pow(i, j)>tmp&&Math.pow(i, j)<=X) {
 
					tmp = (int) Math.pow(i, j);
								}
				if(Math.pow(i, j)>X) {
						break;
				}
 
			}
 
		}
		System.out.println(tmp);
	}
 
}
/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