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 Ruby (2.3.3) (judge verdict: Accepted)

N,K = gets.split.map(&:to_i)
s = gets.strip

if K == 1
  puts s[0].downcase + s[1,N]
elsif K == N
  puts s[0,N-1] + s[N-1].downcase
else
  puts s[0,K-1] + s[K-1].downcase + s[K,N]
end