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;

fn procon_read<T: std::str::FromStr>() ->  Vec<T> {
	let mut buf = String::new();
	io::stdin().read_line(&mut buf).expect("");
	let iter = buf.split_whitespace();
	let mut v: Vec<T> = Vec::new();
	for i in iter {
		v.push(i.parse().ok().unwrap());
	}
	v
}

fn main() {
	let v:Vec<u32> = procon_read();
	let n = v[0];
	let k = v[1];
	let mut buf = String::new();
	io::stdin().read_line(&mut buf).expect("");
	let mut s:Vec<char> = buf.trim().chars().collect();
	for i in 0..(k-1){
		print!("{}", s[i as usize]);
	}
	print!("{}", s[(k-1) as usize].to_lowercase().next().unwrap());
	for i in k..n{
		print!("{}", s[i as usize]);
	}
	println!("");
}