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)

fn main() {
    let nk = read_vec::<usize>();
    let mut v: Vec<char> = {
        let s = read::<String>();
        s.chars().into_iter().collect()
    };
    for i in 0..nk[0] {
        if i == nk[1] - 1 {
            let c = v[i];
            v[i] = to_ascii_lowercase(c);
        }
    }
    let ret: String = v.into_iter().collect();
    println!("{}", ret);
}

fn to_ascii_lowercase(c: char) -> char {
    ((c as u8) | (1 << 5)) as char
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().parse().ok().unwrap()
}