import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
      	//入力
        int x = sc.nextInt();
      	//入力が「1」の場合
        if (x == 1) {
            System.out.println(1);
            return;
        }
        int max = 1;
        for (int i = 2; i <= x; i++) {
          	//※Math.pow(i, j)は「iのj乗」
            for (int j = 2; (int)Math.pow(i, j) <= x; j++) {
            //最大値を出力  
              max = Math.max(max, (int)Math.pow(i, j));
            }
        }
        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