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;

namespace abc126A
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            string[] str = Console.ReadLine().Split();
            int A = int.Parse(str[0]);
            int B = int.Parse(str[1]);
            string C = Console.ReadLine();
            string temp = C.Substring(0, B - 1);
            string hoge = C.Substring(B - 1, 1);
            string moga = C.Substring(B, A - B);
            string mogo = hoge.ToLower();
            Console.WriteLine(temp + mogo + moga);
        }
    }
}