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"
  "strings"
)

var n, k int
var s, ans string

func main() {
  fmt.Scanf("%d%d", &n, &k)
  fmt.Scanf("%s", &s)
  k--
  for i, ch := range s {
    if i == k {
      ans += strings.ToLower(string(ch))
    } else {
      ans += string(ch)
    }
  }
  fmt.Println(ans)
}