using System;

class Replace
{
	static void Main(String[] args)
	{
		long N = long.Parse(Console.ReadLine());
		long sqn = (long)Math.Sqrt(N) + 1;
		for(long i = 3; i <= sqn; i++)
		{
			if(N % i == 0)
			{
				Console.WriteLine(i);
				return;
			}
		}
		Console.WriteLine(N);
	}
}