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)

#include<bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i=0;i<(n);++i)
#define reps(i,n) for(int i=1;i<=(n);++i)
#define repr(i,n) for(int i=(n);i>=0;--i)
#define cinv(n,vec) V vec(n);for(auto&v:vec)cin>>v;
#define int long long
#define itn int
#define pb push_back
#define m_p make_pair
#define m_t meke_tuple
#define p_p(a,b) pb(m_p(a,b))
#define all(a) a.begin(),a.end()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(all(a));reverse(all(a))
#define UNIQUE(a) a.erase(unique(all(a)),a.end())
#define SZ(a) (ll)(a.size())
#define ENDL cout<<endl
#define debg(a) cout<<#a<<" "<<a<<endl;
#define debgp(a) cout<<#a<<" "<<a.fi<<" : "<<a.se<<endl
#define call(a) for(auto i:a)cout<<i<<" ";cout<<endl
#define show(a) rep(ghf,SZ(a)){rep(kjh,SZ(a[ghf])){cout<<(a[ghf][kjh]<10?" ":"")<<a[ghf][kjh]<<" ";}ENDL;}
#define out(a) cout<<(a)<<endl
#define fi first
#define se second
#define Vec vector
#define P pair
#define VV(type,name,y,x,a) vector<vector<type>> name = vector<vector<type>>(y,vector<type>(x,a))
typedef long long ll;
typedef double D;
typedef long double LD;
typedef string str;
typedef vector<ll> V;
typedef pair<ll,ll> Pi;
typedef vector<Pi> VP;
const long long INF = 1LL<<60;
const long long MOD = 1e9+7;
void Yes(){cout<<"Yes"<<endl;}
void No(){cout<<"No"<<endl;}
void YN(bool b){cout<<(b?"Yes":"No")<<endl;}
template<class T>inline T gcd(T a,T b){if(b==0)return a; return(gcd(b,a%b));}
template<class T>inline T lcm(T a,T b){return a/gcd(a,b)*b;}
template<class T>inline bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>inline bool chmin(T &a,const T &b){if(a>b){a=b;return true;}return false;}

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n,k;
  str s;
  cin>>n>>k>>s;
  k--;
  s[k]-='A'-'a';
  out(s);
  
  
  
  
  return 0;
}