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;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        List<int> NK = Console.ReadLine().Split(' ').Select(o => int.Parse(o)).ToList();
        int N = NK[0], K = NK[1];
        List<char> S = Console.ReadLine().ToList();

        K--;
        foreach (var x in S.Select((o, p) => new { Index = p, Value = o }))
        {
            if (x.Index == K)
                Console.Write(char.ToLower(x.Value));
            else
                Console.Write(x.Value);
        }
    }
}