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 static System.Console;

namespace a {
static class Extensions {
   public static int ToInt(this string str) {
      return int.Parse(str);
   }

   public static int[] readIntArr() {
      return ReadLine().Split(' ').Select(int.Parse).ToArray();
   }
}

class Program {
   public static void Main(string[] args) {
      var tmp = Extensions.readIntArr();
      var n = tmp[0];
      var k = tmp[1];
      var s = ReadLine();

      var sb = new System.Text.StringBuilder();
      for (var i = 0; i < n; i++) {
         if (i == k - 1) {
            sb.Append(s[i].ToString().ToLower());
         } else {
            sb.Append(s[i]);
         }
      }

      WriteLine(sb.ToString());
   }
}

}