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

namespace ABC126A
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int N = int.Parse(input[0]);
            int K = int.Parse(input[1]);// int　整数型

            string S = Console.ReadLine();// string　文字型

            string[] answer = new string[N];

            for (int i = 0; i < N; i++)
            {
                answer[i] = S.Substring(i,1);//入力文字をバラバラにする
            }
            int pos = K - 1;//配列の添字は０から始まる　１文字目→０　２文字目→１
            if (answer[pos]=="A")
            {
                answer[pos] = "a";
            }
            if (answer[pos]=="B")
            {
                answer[pos] = "b";
            }
            if (answer[pos]=="C")
            {
                answer[pos] = "c";
            }
            for (int i = 0; i < N; i++)
            {
                Console.Write(answer[i]);
            }
        }
    }
}