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 Go (1.6) (judge verdict: Accepted)

package main

import (
  "fmt"
  "unicode"
)

func main() {
  var n, k int
  var s string
  fmt.Scan(&n, &k, &s)
  runes := []rune(s)
  runes[k-1] = unicode.ToLower(runes[k-1])
  fmt.Println(string(runes))
}