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 (GCC 5.4.1) (judge verdict: Accepted)

#pragma GCC optimize ("O2")
#include<bits/stdc++.h>
#include<unistd.h>
using namespace std;
//#define int long long
#define double long double
#define vec vector
#define vi vector<int>
#define FZ(n) memset((n),0,sizeof(n))
#define FMO(n) memset((n),-1,sizeof(n))
#define unset unordered_set
#define ii pair<int, int>
#define vii vector<ii>
#define F first
#define S second
#define PB push_back
#define ALL(x) begin(x),end(x)
#define SZ(x) ((int)(x).size())
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define FORE(i, a, b) for(int i = (a); i <= (b); i++)
#define FORD(i, a, b) for(int i = (a); i >= (b); i--)
#define bitcount(n) __builtin_popcountll(n)
template <typename T,typename U>
std::pair<T,U> operator+(const std::pair<T,U> & l,const std::pair<T,U> & r) {
  return {l.first+r.first, l.second+r.second};
} 
typedef void (*callback_function)(void); // type for conciseness
const long long ZERO = 0LL;
const long long INF64 = 1e18;
const int INF32 = 1e9;
const int MOD = 1e9 + 7;
const double PI = acos(-1.0L);
const double EPS = static_cast<double>(1e-9);
typedef long long ll;

void FILEIO() {  freopen("in.txt", "r", stdin);  freopen("out.txt", "w", stdout); }
// Init variables here
void input() {
	
}

void solve() {
	int n, k; cin >> n >> k;
	string s; cin >> s;
	s[k-1] = tolower(s[k-1]);
	cout << s << endl;
}

//#undef int
int main() {
//#define int long long
  ios_base::sync_with_stdio(false); cin.tie();
//  FILEIO();
//auto beginProgram = chrono::steady_clock::now();

  //int t; cin >> t;
  //while (t--) 
  {
    input();
    solve();
  }

  //auto endProgram = chrono::steady_clock::now();

  return 0;
}