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;
using static System.Console;
using static System.Math;
class program{
  static void Main(string[] args){
    program p = new program();
    p.Run();
  }
  void Run(){
	int[] inp =  Readint();
    int N = inp[0];
    int K = inp[1];
    string S = ReadLine();
    string s =S.Substring(K-1,1);
    if(s=="A")
      s="a";
    else if(s=="B")
      s="b";
    else{
      s="c";
    }
	S=S.Substring(0,K-1)+s+S.Substring(K,N-K);
    WriteLine(S);
  }

  int[] Readint(){
    string[] s = ReadLine().Split();
    int[] res=new int[s.Length];
    Parallel.For(0,s.Length,i=>{
      res[i]=int.Parse(s[i]);
    });
    return res;
  }
}