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::io;
use std::io::{Read, BufRead};

fn main() {
    let stdin = io::stdin();
    let mut stdin = stdin.lock();

    let (n, k) = {
        let mut input = String::new();
        stdin.read_line(&mut input).unwrap();
        let mut input = input.trim().split_whitespace();
        (
            input.next().unwrap().parse::<usize>().unwrap(),
            input.next().unwrap().parse::<usize>().unwrap(),
        )
    };

    let s = {
        let mut s = Vec::new();
        let mut input = [ 0u8; 1];
        for i in 0..n {
            stdin.read(&mut input).unwrap();
            if i+1 != k {
                s.push( input[0] );
            } else {
                s.push( input[0]+32 );
            }
        }
        String::from_utf8(s).unwrap()
    };


    println!("{}", s);
}