import java.util.*;

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

		int max = 1;
		int x = scan.nextInt();

		for(int i = 1; i <= x; i++){
			int abs = 0;
			for(int j = 2; j <= x; j++){

				abs =(int) Math.pow((double)i, (double)j);

				if(abs > x){
					break;
				}
				if(abs > max){
					max = abs;
				}
			}
		}
		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