Problem:
Score : 100 points

Problem Statement

Snuke prepared 6 problems for a upcoming programming contest.
For each of those problems, Rng judged whether it can be used in the contest or not.

You are given a string S of length 6.
If the i-th character of s is 1, it means that the i-th problem prepared by Snuke is accepted to be used; 0 means that the problem is not accepted.

How many problems prepared by Snuke are accepted to be used in the contest?

Constraints

The length of S is 6.

S consists of 0 and 1.

Inputs

Input is given from Standard Input in the following format:

S

Outputs

Print the number of problems prepared by Snuke that are accepted to be used in the contest.

Sample Input 1

111100

Sample Output 1

4

The first, second, third and fourth problems are accepted, for a total of four.

Sample Input 2

001001

Sample Output 2

2

Sample Input 3

000000

Sample Output 3

0

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

using System;
class Program
{
      public static int CountChar(string s, char c) {
    return s.Length - s.Replace(c.ToString(), "").Length;
  }
	static void Main(string[] args)
	{
        /*
		// 整数の入力
		int a = int.Parse(Console.ReadLine());
		// スペース区切りの整数の入力
		string[] input = Console.ReadLine().Split(' ');
		int b = int.Parse(input[0]);
		int c = int.Parse(input[1]);
		// 文字列の入力
		string s = Console.ReadLine();
		//出力
		Console.WriteLine((a+b+c) + " " + s);
        */

        System.Console.WriteLine(CountChar(Console.ReadLine(), '1'));
	}
}