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 a;
  cin >> a;
  string N;
  cin >> N;
  string m=N;
  bool answer=false;
  int count1=0,count2=0; 
   for(int i=0;i<a-1;i++){
  if(N.at(i)=='#'&&N.at(i+1)=='.'){
  break;
  }
  if(i=a-1)
  answer = true;
  }
   if(answer==true){
   cout << 0 <<endl;
   }
   else{  
  for(int i=0;i<a;i++){
  if(N.at(i)=='#'){
  N.at(i)='.';
  count1++;  
  }
   for(int j=0;j<a-1;j++){
  if(N.at(j)=='#'&&N.at(j+1)=='.'){
  break;
    if(j==a-2){
    answer=true;
    }
  } 
  }
    if(answer){
    break;
    }
  }
     answer=false;
    for(int i=a-1;i>=0;i--){
  if(m.at(i)=='.'){
  m.at(i)='#';
  count2++;  
  }
   for(int j=0;j<a-1;j++){
  if(N.at(j)=='#'&&N.at(j+1)=='.'){
  break;
    if(j==a-2){
    answer=true;
    }
  } 
   }
      if(answer){
      break;
      }
    }
     if(count1<count2){
     cout << count1 << endl;
     }     
     if(count2<count1){
     cout << count2 << endl;
     }
  
  }
}