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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
#define INF 1e9
 
int main() {
  int N;
  string S;
  cin >> N >> S;
 
  char state = S[0];
  int count = 0;
  vector<int> count_list;
  
  for (int i = 0; i < N; i++) {
    if (S[i] == state) {
      count++;
    } else {
      count_list.push_back(count);
      state = S[i];
      count = 1;
    }
  }
  count_list.push_back(count);
 
  bool start = S[0] == '.' ? false : true;
  if (S[N-1] == '#') {
    count_list[count_list.size()-1] = 0;
  }
 
  count = 0;
  if (S[0] == '.') {
    int count_white = 0;
    for (int i = 1; i < count_list.size(); i++) {
      if (i % 2 == 0) count_white += count_list[i];
    }
    int count_black = 0;
    for (int i = 1; i < count_list.size(); i++) {
      if (i % 2 == 1) count_black += count_list[i];
    }
    count = min(count_white, count_black);
  } else {
    int count_black = 0;
    for (int i = 0; i < count_list.size(); i++) {
      if (i % 2 == 0) count_black += count_list[i];
    }
    int count_white = 0;
    for (int i = 0; i < count_list.size(); i++) {
      if (i % 2 == 1) count_white += count_list[i];
    }
    count = min(count_white, count_black);
  }
 
  cout << count << endl;
  return 0;
}