import java.util.Scanner;

public class Test {
	public static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		long n = sc.nextLong(), m = 0;
		while ((m + 100000) * (m + 100000) <= n) {
			m += 100000;
		}
		while ((m + 10000) * (m + 10000) <= n) {
			m += 10000;
		}
		while ((m + 1000) * (m + 1000) <= n) {
			m += 1000;
		}
		while ((m + 100) * (m + 100) <= n) {
			m += 100;
		}
		while ((m + 10) * (m + 10) <= n) {
			m += 10;
		}
		while ((m + 1) * (m + 1) <= n) {
			m++;
		}
		boolean[] b = new boolean[(int)m + 1];
		for (int i = 3; i <= m; i++) {
			if (!b[i]) {
				if (n % (long) i == 0) {
					System.out.println(i);
					return;
				}
				for (int j = i * 2; j <= m; j += i) {
					b[j] = true;
				}
			}
		}
		if(n > 4 && n % 2 == 0){
			System.out.println(n/2);
		} else {
			System.out.println(n);
		}
	}
}