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

    ll w = 0;
    ll b = 0;

    bool flag = false;
    for(ll i=0; i<n; i++){
        if(s[i] == '.'){
            if(flag){
                w++;
            }
        }else{
            b++;
            flag = true;
        }
    }
    ll bl;
    if(s[n-1] == '#'){
        for(ll i=0; i<n; i++){
            if(s[n-1-i] == '#'){
                bl++;
            }else{
                break;
            }
        }
        if(min(b-bl, w)==b - bl){
            b = b - bl;
        }
        // cout << bl << endl;
    }

    ll ans = min(w, b);

    cout << ans << endl;
    return 0;
}