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 (Clang 3.8.0) (judge verdict: Runtime Error)

#include <stdio.h>

int main(){
  int n;
  scanf("%d",&n);
  
  int u[n],v[n],w[n],ans[n+1];
  for(int i=1;i<n;i++){
    scanf("%d %d %d",&u[i],&v[i],&w[i]);
    ans[i]=2;
  }
  ans[n]=2;
  
  ans[u[1]]=0;
  ans[v[1]]=w[1]%2;
  
  for(int i=2;i<n;i++){
    if(ans[u[i]]==2){
      if(ans[v[i]]==2){
        ans[v[i]]=w[i]%2;
      }else{
        ans[u[i]]=(w[i]+ans[v[i]])%2;
      }
    }
    if(ans[v[i]]==2){
      if(ans[u[i]]==2){
        ans[u[i]]=w[i]%2;
      }else{
        ans[v[i]]=(w[i]+ans[u[i]])%2;
      }
    }
  }
  
  for(int i=1;i<=n;i++){
    printf("%d\n",ans[i]);
  }
  return 0;
}