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.Collections.Generic;
using static AtCoderer.Exter;
using System.Linq;

namespace AtCoderer
{

    public class App
    {
        public static void Main(string[] args)
        {
            int i = 0;
            int s = readarr[1]-1;
            foreach (var c in Console.ReadLine())
            {
                if (s == i)
                    Console.Write(char.ToLower(c));
                else
                    Console.Write(c);
                    i++;
            }
            Console.WriteLine();
            Console.ReadLine();
        }
    }
    public static class Exter
    {
        public static void rep(int loop, Action<int> act)
        {
            for (int i = 0; i < loop; i++)
                act(i);
        }
        public static int ToInt(this string v) => int.Parse(v);
        public static int Max(params int[] p) => p.Max();
        public static long Max(params long[] p) => p.Max();
        public static int Min(params int[] p) => p.Min();
        public static long Min(params long[] p) => p.Min();
        public static int Gcd(int a, int b) => a > b ? GcdRecursive(a, b) : GcdRecursive(b, a);
        private static int GcdRecursive(int a, int b) => b == 0 ? a : GcdRecursive(b, a % b);
        public static object cout
        {
            set
            {
                Console.Write(value.ToString());
                Console.WriteLine();

            }
        }
        public static void ToCout<t>(this IEnumerable<t> v)
        {
            cout = string.Join(",", v);
        }
        public static int[] readarr
        {
            get
            {
                preadarr = Console.ReadLine().Split().Select(s => int.Parse(s)).ToArray();
                return preadarr;
            }
        }
        public static int[] preadarr;
    }
}