import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		
		int a = 1;
		
		for(int i = 2; i <= 32; i++) {
			for(int j =2; j <=10; j++) {
				double b = Math.pow(i, j);
				if(b <= X) {
					if(X - a >= X - b) {
						a = (int)b;
					}
				} else {
					break;
				}
			}
		}
		if(X < 4) {
			System.out.println(X);
		} else {
			System.out.println(a);
		}
	}
}

/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