using System;

namespace No312
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			long n = Convert.ToInt64 (Console.ReadLine ());

			for (long i = 3; i * i <= n; i++) {
				if (n % i == 0) {
					Console.WriteLine (i.ToString ());
					return;
				}
			}
			Console.WriteLine (n.ToString ());
		}
	}
}