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

class Main {
	
	public static void out (Object o) {
		System.out.println(o);
	}
	
	public static long solve (long n) {
		long k = n;
		while (k % 2 == 0) k /= 2;
		if (k == 1) return 4;
		
		for (int i = 3; i * i <= n; i += 2) {
			if (n % i == 0) return i;
		}
		return n;
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		long n = Long.parseLong(br.readLine());
		
		out(solve(n));
	}
}