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>
#define ll long long
#define IOS ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define mp make_pair
#define pb push_back
#define mod 1000000007

using namespace std;

int main() {
    IOS;
  ll n,k;
  cin>>n;
  string s;
  cin>>s;
  int cntb=0,cntw=0,flag=1,ans=0;
  for(int y=0;y<n;y++)
  {
        if(s[y]=='.')
            continue;
        else
        {
            cntb=1;
            y++;
            while(s[y]=='#' && y<n)
            {
                y++;
                cntb++;
            }
            while(s[y]=='.' && y<n)
            {
                y++;
                cntw++;
            }
            if(cntb<=cntw)
            {
                ans+=cntb;
                y--;
            }
            else
            {
                int tempb=0,tempw=0;
                while(y<n)
                {
                    if(s[y]=='.')
                        tempw++;
                    else
                        tempb++;
                    y++;
                }
                if(tempw>tempb)
                    ans+=tempb+cntb;
                else
                    ans+=tempw+cntw;
            }
        }
        cntw=0,cntb=0;
  }
  cout<<ans<<"\n";

    return 0;
}