import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
    
		// 整数の入力
		int x = sc.nextInt();
		int ans = 1;
        int b = 1;
      
        if (x == 1) {
          // 出力
		  System.out.println(ans);
          return;
        }
      
        Parent: while(true) {
          b++;
          if (Math.pow(b, 2) > x) {
            break Parent;
          }
          int p = 2;
          Child: while(true) {
            int value = (int)Math.pow(b, p);
            if (value > x) {
              break Child;
            } else if (value > ans) {
              ans = value;
            }
            p++;
          }
        }
    
		// 出力
		System.out.println(ans);
	}
}
/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