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 Rust (1.15.1) (judge verdict: Wrong Answer)

use std::io::stdin;

fn main() {
    let mut s = String::new();
    let mut buffer = String::new();
    stdin().read_line(&mut s).unwrap();
    stdin().read_line(&mut buffer).unwrap();
    buffer = buffer.trim().to_string();
    let arg = s.trim().split_whitespace().map(|x| x.parse::<usize>().unwrap()).collect::<Vec<_>>();
    if arg[1] < arg[0] {
        buffer = buffer.chars().enumerate().map(|(i,x)| if i == arg[1]-1 {
            x.to_lowercase().nth(0).unwrap()
        } else { x }).collect::<String>();
    } 
    println!("{}", buffer);
}