Problem:
Score : 100 points

Problem Statement

You are given a string S of length N consisting of A, B and C, and an integer K which is between 1 and N (inclusive).
Print the string S after lowercasing the K-th character in it.

Constraints

1 ≤ N ≤ 50

1 ≤ K ≤ N

S is a string of length N consisting of A, B and C.

Input

Input is given from Standard Input in the following format:

N K
S

Output

Print the string S after lowercasing the K-th character in it.

Sample Input 1

3 1
ABC

Sample Output 1

aBC

Sample Input 2

4 3
CABA

Sample Output 2

CAbA

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

using System;
using System.Linq;

namespace A
{
    class Program
    {
        static void Main(string[] args)
        {
            var NK = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            var N = NK[0];
            var K = NK[1];
            var S = Console.ReadLine();

            var output = "";
            foreach (var i in Enumerable.Range(0, N))
            {
                if (i == K - 1)
                {
                    output += new string(new[] { S[i] }).ToLower()[0];
                }
                else
                {
                    output += S[i];
                }
            }

            Console.WriteLine(output);
        }

        static int NumberOfDigits(long x)
        {
            if (x < 10) return 1;

            var result = 0;
            while (x > 0)
            {
                result++;
                x /= 10;
            }

            return result;
        }

        static int SumOfDigits(int x)
        {
            var sum = 0;
            while (x > 0)
            {
                sum += x % 10;
                x /= 10;
            }

            return sum;
        }
    }
}