import java.util.*;
 
public class Main {
 	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
		int X = sc.nextInt();
		int max = 0;

		if(X!=1){
			for(int b=2; b<Math.sqrt(X); b++){
				int p=2;
				int pow = (int) Math.pow(b,p);
				while(pow<=X){
					if(max<pow){
						max=pow;
					}
					p++;
					pow = (int) Math.pow(b,p);
				}
			}
		}else{
			System.out.println("1");
			return;
		}
		System.out.println(max);
    }
}
/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