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;

int main()
{
  int n;
  string s;
  cin >> n >> s;
  int i;
  int point = 1000000;
  int countb = 0;
  int chantob = 0;
  int ch = 0;
  if(s.at(0) == '#')
  {
    ch = 1;
  }
  for(i = 0; i < n; i++)
  {
    if(s.at(i) == '#')
    {
      point = i;
      break;
    }
  }
  int countw = 0;
  for(i = 0; i < n; i++)
    {
      if(s.at(i) == '#')
      {
        countb++;
      }
      else
      {
        countw++;
      }
    }
  
  for(i = 0; i < n; i++)
  {
    if(i > point && s.at(i) == '.')
    {
      chantob++;
    }
  }
  if(ch = 1)
  {
    cout << min(countb, countw) << endl;
  }
  else
  {
    cout << min(countb, chantob) << endl;
  }
}