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.Collections.Generic;
using System;
using static System.Console;

namespace atcoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var NK = Input.ar;
            int pos = NK[1] - 1;
            var S = Input.read;


          string outt=  S.Substring(0, pos<0?0:pos) + Char.ToLower(S[pos])
                + S.Substring(NK[1] );
            System.Console.WriteLine(outt);
        }
        public class Input
        {
            
            public static string read => ReadLine();
            public static int[] ar => Array.ConvertAll(read.Split(' '), int.Parse);
            public static int num => Convert.ToInt32(read);
            public static long[] arL => Array.ConvertAll(read.Split(' '), long.Parse);
            public static long numL => Convert.ToInt64(read);
            public const string Alfa = "abcdefghijklmnopqrstuvwxyz";
            public const int MOD = 1000000007;
        }
    }
}