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.Threading.Tasks;
 
static class Program
{
static void Main()
{
   ulong replaceIdx = Console.ReadLine().Split(' ').Select(c => ulong.Parse(c)).Skip(1).First();
   var inputStr = Console.ReadLine().ToArray();
   inputStr[replaceIdx-1] = Char.ToLower(inputStr[replaceIdx-1]);
   Console.WriteLine(string.Join("",inputStr));
}
}