Problem:
Score : 100 points

Problem Statement

Snuke has a grid consisting of three squares numbered 1, 2 and 3.
In each square, either 0 or 1 is written. The number written in Square i is s_i.

Snuke will place a marble on each square that says 1.
Find the number of squares on which Snuke will place a marble.

Constraints

Each of s_1, s_2 and s_3 is either 1 or 0.

Input

Input is given from Standard Input in the following format:

s_{1}s_{2}s_{3}

Output

Print the answer.

Sample Input 1

101

Sample Output 1

2

A marble will be placed on Square 1 and 3.

Sample Input 2

000

Sample Output 2

0

No marble will be placed on any square.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoderTest
{
    class PlacingMarbles
    {
        static int countFromString(string inStr)
        {
            int res = 0;
            for (int i=0; i<3; ++i)
                if (int.Parse(inStr.Substring(i, 1)) > 0)
                    res++;

            return res;
        }

        public static string core()
        {
            var inStr = Console.ReadLine();
            var retStr = countFromString(inStr).ToString();
            return retStr;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Console.Write(PlacingMarbles.core());
        }
    }

}