import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int X = Integer.parseInt(br.readLine());
		List<Integer> beki = new ArrayList<Integer>();
		beki.add(1);

		for(int i = 2;i<32;i++){
			int p = 2;
			int now = (int)Math.pow(i, p);
			while(now <= X){
				beki.add(now);
				p++;
				now = (int)Math.pow(i, p);

			}
		}

		beki.sort(null);
		System.out.println(beki.get(beki.size()-1));

	}


}
/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