import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		double X = sc.nextDouble();
      	double i;
      	double j;
      	int count = 0;
      	for(i = 1; i <= X / 2 + 1; i++){
          for(j = 1; j <= X / 2 + 1; j++){
            if(count <= (int) Math.pow(i, j) && (int) Math.pow(i, j) <= X){
              count = (int) Math.pow(i, j);
            }
          }
        }
        System.out.println(count);  
    }
}
/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