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: Runtime Error)

using System;
using System.Linq;

class abc126{
  static void Main(){
    var IN=Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
    var N=IN[0];
    var K=IN[1];
    var S=Console.ReadLine();
    
    var result = "";
    
    for(int i=0;i<N;i++){
      if(i-1==K){
        if(S[i-1].Equals('A'))
          {
            result=result+"a";
          }
        if(S[i-1].Equals('B'))
          {
            result=result+"b";
          }
        if(S[i-1].Equals('C'))
          {
            result=result+"c";
          }
      }
      else
      {
        result=result+S[i-1];
      }
    }
    
    Console.WriteLine(result);
    
    return;
  }
}