import java.util.*;
import java.io.*;

public class Main {

	public static void main(String[] args) throws IOException {
		
		// 入出力高速化 java.io.* とthrows IOExceptionを忘れずに
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int X = Integer.parseInt(br.readLine());
		long ans = 0;
		for(int x=1; x<32; x++) {
			for(int b=2; b<=10; b++) {
				int B = (int)Math.pow(x, b);
				if(B<=X) {
					if(B>ans) {
						ans=B;
					}
				}else{
					break;
				}
			}
		}
		
		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