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 Perl (v5.18.2) (judge verdict: Accepted)

my ($n, $k) = split(/\s+/, <>);
my ($s) = split(/\s+/, <>);

for my $i (0..($n-1)) {
    my $c = substr($s, $i, 1);
    if ($i+1 == $k) {
	$c =~ tr/A-Z/a-z/;
    }
    print $c;
}
print "\n";