import java.util.Scanner;

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

		int X = sc.nextInt();
		int ans = 0;
		
		for (int i = 1; i < 33; i++){
			
			int tmp = i;
			
			for (int j = 0; j < 9; j++){
				tmp *= i;
				
				if (ans < tmp && tmp <= X){
					ans = tmp;
			}
			
			}

		}
		
		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