import java.util.*;
public class Main {
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int x=Integer.parseInt(sc.next());
double temp=0;
for(int i=1;i<32;i++){
for(int j=2;j<10;j++){
    if(Math.pow(i,j)<=x){
        
temp=Math.max(temp,Math.pow(i,j));
        }
        }
}
int ans=(int)temp;
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