import java.security.cert.CollectionCertStoreParameters;
import java.util.*;

public class Main {

    public static void main(String args[]) {

        // 入力
        Scanner sc = new Scanner(System.in);
        int x = Integer.parseInt(sc.next());
        sc.close();

        // 主処理
        int maxRoot = (int) Math.sqrt(1000);
        List<Integer> list = new ArrayList<>();
        list.add(1);
        for (int i = 2; i <= maxRoot; i++) {
            int num = i * i;
            while (num <= 1000) {
                list.add(num);
                num *= i;
            }
        }
        Collections.sort(list);

        int result = 0;
        for (int num : list) {
            if (x < num) {
                break;
            }
            result = num;
        }

        // 出力
        System.out.println(result);
    }
}

/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