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 Lua (Lua 5.3.5) (judge verdict: Accepted)

n, k = io.read("*n", "*n", "*l")
s = io.read()
for i = 1, n do
  if i == k then
    io.write(string.char(s:byte(k) + 32))
  else
    io.write(s:sub(i, i))
  end
end
io.write("\n")