import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    boolean[] b = new boolean[1001];
    b[1] = true;
    for (int i = 2; i <= 32; i++) {
      int tmp = i * i;
      while (tmp <= 1000) {
        b[tmp] = true;
        tmp *= i;
      }
    }

    int x = sc.nextInt();
    int i = x;
    while (true) {
      if (b[i]) {
        System.out.println(i);
        return;
      }
      i--;
    }

  }
}
/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