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 PyPy3 (2.4.0) (judge verdict: Accepted)

from sys import stdin
import math
import fractions
from collections import deque

INF = 10 ** 10

N, K = [int(x) for x in stdin.readline().rstrip().split()]
S = stdin.readline().rstrip()

ans = ""
for i in range(N):
    if i == K-1:
        ans += str(S[i]).lower()
    else:
        ans += S[i]

print(ans)