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 C++14 (Clang 3.8.0) (judge verdict: Accepted)

#include <iostream>
#include<algorithm>
#include<string>
#include <cmath>
#include <vector>
#pragma region Macros
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(i,n) for(int i=1;i<=n;i++)
#define int long long
#define all(x) (x).begin(),(x).end()
#define swap(a,b) (a += b,b = a - b,a -= b)
int gcd(int a, int b) // assuming a,b >= 1
{
    if (a < b)
        swap(a, b);
    if (b == 0)
        return a;
    if (a % b == 0)
        return b;
    return gcd(b, a % b);
}
int lcm(int a, int b) // assuming a,b >= 1
{
    return  a * b / gcd(a, b);
}
using namespace std;
#pragma endregion
signed main() {
    int N,K;
    string S;
    cin >> N >> K >> S;
    S[K - 1] = S[K-1]+32;
    cout << S;
}