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: Runtime Error)

if s_former.to_i.between?(01,12 ) && s_latter.to_i.between?(01, 12)
    puts "AMBIGUOS"
end

if s_former.to_i.between?(01,12 ) && ( s_latter.to_i.between?(13, 99) || s_latter.to_i == 00 )
    puts "MMYY"
end

if s_latter.to_i.between?(01,12 ) && ( s_former.to_i.between?(13, 99) || s_former.to_i == 00 )
    puts "YYMM"
end

if ( s_former.to_i.between?(13, 99) || s_former.to_i == 00 ) && ( s_latter.to_i.between?(13, 99) || s_latter.to_i == 00 )
    puts "NA"
end