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: Wrong Answer)

require 'bigdecimal'
 
N, K = gets.chop.split.map(&:to_i)
 
@sum = 0
 
(1..N).to_a.each do |i|
  now = i
  probability = Rational(1, N)
  while now < K do
    now *= 2
    probability *= Rational(1, 2)
  end
  @sum += probability
end
 
puts @sum.to_f