using System;

public class Test
{
	public static void Main()
	{
		var x = Console.ReadLine();
		
		int ans = 0;
		foreach(var c in x)
		{
			int n = 0;
			var s = Int32.TryParse(c.ToString(), out n);
			ans += n;
		}
		Console.WriteLine(ans);
	}
}