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: Wrong Answer)

using System;
class Program
    {
        static void Main(string[] args)
        {
            //数の導入
            string str = Console.ReadLine();
            int[] test = new int[2];

            //二つに分離する
            for (int i = 0; i < str.Length - 1; i += 2)
            {
                test[i / 2] = int.Parse(str.Substring(i, 2));
            }

            //判定を行う
            int judge1 = 0;
            int judge2 = 0;
            //条件1を満たすか
            if (1 <= test[0] && test[0] <= 12)
                judge1 = 1;

            //条件2を満たすか
            if (1 <= test[1] && test[1] <= 12)
                judge2 = 1;

            //条件分離
            if (judge1 == 1 && judge2 == 1)
                Console.WriteLine("AMBIGUOUS");
            else if (judge1 == 1 && judge2 == 0)
                Console.WriteLine("MMYY");
            else if (judge1 == 0 && judge2 == 1)
                Console.WriteLine("YYMM");
            else
                Console.WriteLine("NA");

        }
    }