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 Python (3.4.3) (judge verdict: Runtime Error)

import sys
 
args = sys.argv
 
length = args[1]
focus = args[2]
abcs = args[3]
 
 
def change_upper_to_lower(str, num):
  if(str[int(num)] == "A"):
    str[int(num)] = "a"
  elif(str[int(num)] == "B"):
    str[int(num)] = "b"
  else:
    str[int(num)] = "c"
    
  return str
 
 
changed_abcs = change_upper_to_lower(abcs, focus)
 
print(changed_abcs)