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: Accepted)

use std::ascii::AsciiExt;
use std::io::{stdin, BufReader, StdinLock, BufRead};

fn main() {
    let std_in = stdin();
    let mut br = BufReader::new(std_in.lock());

    let tmp: Vec<usize> = rvn(&mut br);
    let (n, k) = (tmp[0], tmp[1]);
    let mut s = rs(&mut br);
    s[k-1] = s[k-1].to_ascii_lowercase();
    for c in s {
        print!("{}", c);
    }
    println!();
}


//////////////////////////////////////////////////////////////////////////////////

fn rs(br: &mut BufReader<StdinLock>) -> Vec<char> {
    let mut buf = String::new();
    br.read_line(&mut buf).ok();
    buf.trim().chars().collect()
}

fn rn<T: std::str::FromStr>(br: &mut BufReader<StdinLock>) -> T {
    let mut buf = String::new();
    br.read_line(&mut buf).ok();
    buf.trim().parse().ok().unwrap()
}

fn rvs(br: &mut BufReader<StdinLock>) -> Vec<Vec<char>> {
    let mut buf = String::new();
    br.read_line(&mut buf).ok();
    buf.trim().split_whitespace().map(|e| e.chars().collect()).collect()
}

fn rvn<T: std::str::FromStr>(br: &mut BufReader<StdinLock>) -> Vec<T> {
    let mut buf = String::new();
    br.read_line(&mut buf).ok();
    buf.trim().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}