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 <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;

int main()
{
    ll n;
    string str;
    cin >> n >> str;
    ll count = 0, count1 = 0, count2 = 0;
    bool found = false;
    ll limit = n;
    for (ll i = n-1; (i >= 0); --i) {
        if (str[i] != '#') {
            limit = i+1;
            break;
        }
    }
    for (ll i = 0; (i < limit); ++i) {
        if (str[i] == '#') {
            count++;
            found = true;
        }
        if (str[i] == '.') {
            count1++;
        }
        if (found && str[i] == '.') {
            count2++;
        }
    }
    ll result = min(count, count1);
    result = min(result, count2);
    cout << result << endl;
    return 0;
}