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;
    cin >> n;
    string s;
    cin >> s;

    int flagwhite = 0;
    int flagblack = 0;

    for (int i = 0; i < n - 1; i++)
    {
        if (s.at(i) == '.')
        {
            flagwhite++;
        }
        else if (s.at(i) == '#')
        {
            flagblack++;
        }
    }
    if (s.at(n - 1) == '.')
    {
        flagwhite++;
        if (flagblack <= flagwhite)
        {
            cout << flagblack << endl;
        }
        else
        {
            cout << flagwhite << endl;
        }
    }
    else if (s.at(n - 1) == '#')
    {
        if (flagblack <= flagwhite)
        {
            cout << flagblack << endl;
        }
        else
        {
            cout << flagwhite << endl;
        }
    }

    return 0;
}