Problem:
Score : 200 points

Problem Statement

Find the sum of the integers between 1 and N (inclusive), whose sum of digits written in base 10 is between A and B (inclusive).

Constraints

1 \leq N \leq 10^4

1 \leq A \leq B \leq 36

All input values are integers.

Input

Input is given from Standard Input in the following format:

N A B

Output

Print the sum of the integers between 1 and N (inclusive), whose sum of digits written in base 10 is between A and B (inclusive).

Sample Input 1

20 2 5

Sample Output 1

84

Among the integers not greater than 20, the ones whose sums of digits are between 2 and 5, are: 2,3,4,5,11,12,13,14 and 20. We should print the sum of these, 84.

Sample Input 2

10 1 2

Sample Output 2

13

Sample Input 3

100 4 16

Sample Output 3

4554

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

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;

namespace PastQuestions
{
    class Program
    {
        static void Main(string[] args)
        {
            new Program().Solve(new Input(Console.In));
        }

        public void Solve(Input input)
        {
            var n = input.ReadInt;
            var a = input.ReadInt;
            var b = input.ReadInt;

            var answer = 0;
            for (var i = 1; i <= n; ++i)
            {
                var iArr = i.ToString().ToArray();
                var total = 0;
                for (var j = 0; j < iArr.Length; j++)
                {
                    total += int.Parse(iArr[j].ToString());
                }
                if (a <= total && total <= b)
                    answer += i;
            }

            Console.WriteLine(answer);
        }
    }

    public class Input
    {
        private TextReader Stream { get; }
        private char Separator { get; }
        private Queue<string> InputStream { get; }

        public Input(TextReader stream, char separator = ' ')
        {
            Stream = stream;
            Separator = separator;
            InputStream = new Queue<string>();
        }

        public string Read
        {
            get
            {
                if (InputStream.Count != 0) return InputStream.Dequeue();
                string[] tmp = Stream.ReadLine().Split(Separator);
                for (int i = 0; i < tmp.Length; ++i)
                    InputStream.Enqueue(tmp[i]);
                return InputStream.Dequeue();
            }
        }

        public string ReadLine => Stream.ReadLine();
        public int ReadInt => int.Parse(Read);
        public long ReadLong => long.Parse(Read);
        public double ReadDouble => double.Parse(Read);
        public long[] ReadLongArray => Stream.ReadLine().Split(Separator).Select(l => long.Parse(l)).ToArray();
    }
}