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 <algorithm>
#include <cctype>
#include <cstdio>
#include <iostream>
#include <locale>
#include <numeric>
#include <string>
#include <vector>

using namespace std;

int main() {
    cin.tie(0);
    long n;
    string s;
    cin >> n;
    cin >> s;
    long minsharp = n;
    for (int i = 0; i < n; i++) {
        if (s[i] == '#') {
            minsharp = i;
            break;
        }
    }
    long answ = 0;
    for (int i = minsharp; i < n; i++) {
        if (s[i] == '#') answ++;
    }

    minsharp = n;
    for (int i = 0; i < n; i++) {
        if (s[i] == '#') {
            minsharp = i;
            break;
        }
    }
    long ansb = 0;
    for (int i = minsharp; i < n; i++) {
        if (s[i] != '#') ansb++;
    }

    cout << min(ansb, answ) << endl;
    return 0;
}