import java.util.*;
 
public class Main{
	public static void main(String[] args){
	    Scanner sc = new Scanner(System.in);
    	int num = sc.nextInt();
        int e = 0;
        for(int i = 1; i < num + 1; i++){
            if(num == 1){
            	e = 1;
            }else{
        		for(int j = 2; j < num; j++){
            		if((Math.pow(i,j) <= num) && (e < Math.pow(i,j))){
                		e = (int)Math.pow(i,j);
                	}
            	}
            }
        }
        System.out.println(e);
	}
}
/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