import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int x = in.nextInt();
        boolean[] a = new boolean[x+1];
        a[1] = true;
        for(int i = 2; i < x; i++) {
            int t = i * i;
            while(t <= x) {
                a[t] = true;
                t *= i;
            }
        }
        int ans = x;
        while(!a[ans]) ans--;
        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