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;
fn main() {
    let mut buf = String::new();
    let _ = std::io::stdin().read_line(&mut buf);
    let nk = buf.split_whitespace().map(|x|x.parse().unwrap()).collect::<Vec<usize>>();
    let k = nk[1];
    buf.clear();
    let _ = std::io::stdin().read_line(&mut buf);
    print!("{}", buf.chars().take(k-1).collect::<String>());
    print!("{}", buf.chars().nth(k-1).unwrap().to_ascii_lowercase());
    print!("{}", buf.chars().skip(k).collect::<String>());
    println!();
}