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)

#![allow(unused_imports)]
#[macro_use]
mod reader {
    // mod calc;

    // use calc::*;


    #![allow(dead_code)]
    use std;
    macro_rules! read_line((  ) => {
                           {
                           let mut input = String :: new (  ) ; std :: io ::
                           stdin (  ) . read_line ( & mut input ) . unwrap (
                           ) ; input } } ;);
    pub fn read_to_vec<T: std::str::FromStr>() -> Vec<T> {
        read_line!().split_whitespace().map(|e|
                                                e.parse().ok().unwrap()).collect()
    }
    pub fn read_trim() -> String { read_line!().trim().to_owned() }
}
#[macro_use]
mod misc {
    #![allow(dead_code)]
    use std;
    #[macro_export]
    macro_rules! bind_from_vec((
                               $ ( $ variable : ident ) , + = $ vector : expr
                               ) => {
                               let mut v = $ vector . clone (  ) . into_iter (
                                ) ; $ (
                               let $ variable = v . next (  ) . unwrap (  ) ;
                               ) + } ;);
}
use reader::*;
use misc::*;
fn main() {
    bind_from_vec!(_n , k = read_to_vec :: < usize > (  ));
    let input = read_trim();
    let former = &input[..k - 1];
    let mid = &input[k - 1..k].to_lowercase();
    let latter = &input[k..];
    println!("{}{}{}" , former , mid , latter);
}