import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


class Main {
    public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int x = sc.nextInt();
    	int xx = x / 2;
    	int ans = 0;

    	for(int i = 1; i <= x; i++){
    		for(int j = 2; j <= x + 1; j++){
    			if(Math.pow(i, j) > ans && Math.pow(i, j) <= x){
    				ans = (int)Math.pow(i, j);
    			}
    		}
    	}

    	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