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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>

#define irep(i,n) for(int i = 0; i < (int)(n); i++)
#define irep2(i,a,n) for(int i = (int)(a); i <= (int)(n); i++)
#define irrep(i,n) for(int i = (int)(n-1); i > -1; i--)
#define irrep2(i,n,a) for(int i = (int)(n); i >= (int)(a); i--)

#define fi first
#define se second

using namespace std;

using ll = long long;
using v_int = vector<int>;
using v2_int = vector<v_int>;
using v_ll = vector<ll>;
using v2_ll = vector<v_ll>;
using v_string = vector<string>;
using v_bool = vector<bool>;
using v2_bool = vector<v_bool>;
using pii = pair<int, int>;
using mii = map<int, int>;

const double PI = 3.1415926535897932;
const int INF = (int)2e9;
const ll LINF = (ll)2e18;
const ll MOD = 1000000007;
const int dc[8] = {1, -1, 0,  0, 1, -1,  1, -1};
const int dr[8] = {0,  0, 1, -1, 1,  1, -1, -1};

template<typename T, typename U> inline
ostream& operator<<(ostream &o, pair<T,U> &p) {
    return o << "{" << p.first << "," << p.second << "}";
}
template<typename T> inline
istream& operator>>(istream &is, vector<T> &vec) {
    for(auto &v : vec) { is >> v; }
    return is;
}
template<typename T> inline
ostream& operator<<(ostream &os, vector<T> &vec) {
    for(auto &v : vec) { os << v << ",";}
    return os;
}
template<typename T> inline
ostream& operator<<(ostream &os, vector<vector<T> > &mat) {
    for(auto &row : mat) { os << row << endl; }
    return os;
}
template<typename T> inline
void chmin(T &a, T b) { a = min(a, b); }
template<typename T> inline
void chmax(T &a, T b) { a = max(a, b); }

int main(void)
{
    int n, k;
    cin >> n >> k;

    string s;
    cin >> s;

    s[k-1] = tolower(s[k-1]);

    cout << s << endl;

    return 0;

} /*atcoder*/