Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main()
{
  int i,j;
  int N;
  int cnt,cnt_1=0,cnt_2=0,cnt_b=0;
  scanf("%d",&N);
  char S[N+1];
  scanf("%s",S);
  
  for(i=0; i<N-2; i++){
  	if(S[i]=='#'){
      if(S[i+1]=='.' && S[i+2]=='#'){
        cnt_1++;}
      else if(S[i+1]=='.' && S[i+2]=='.'){
        cnt_1+=2;
        for(j=i+2; j<N; j++){
          if(S[j+1]=='.')
            cnt_1++;
          else break;}
      }
    }
  }
    if(S[N-2]=='#' && S[N-1]=='.')
      cnt_1++;
  
  for(i=N-1; i>=0; i--){
  	if(S[i]=='#')
      cnt_b++;
    if(S[i]=='.')
      break;
  }
  for(i=0; i<N; i++)
    if(S[i]=='#')
      cnt_2++;
  
  if(cnt_1<cnt_2-cnt_b)
    cnt=cnt_1;
  else
    cnt=cnt_2-cnt_b;

  printf("%d",cnt);
  return 0;
}