import java.io.*;
import java.util.*;
import java.math.BigInteger;
public class Main {

static long[] list=new long[87];

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

   String nyuA=sc.nextLine();
int X=Integer.parseInt(nyuA);

int ans=1;

for(int b=2;b<=X;b++){
int power=b*b;
for(int p=2;;p++){
if(power>X)break;
ans=Math.max(ans,power);
power*=b;
}
}
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