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 <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <queue>
#include <utility>
#include <map>
#include <bitset>
#include <numeric>
#define ll long long
using namespace std;
using p = pair<ll, ll>;
ll dx[8]={ 0, 1, 0,-1, 1, 1,-1,-1}; // x軸方向への変位
ll dy[8]={ 1, 0,-1, 0, 1,-1, 1,-1}; // y軸方向への変位

int main(void) {
    ll n;
    cin >> n;
    string s;
    cin >> s;
    ll now = 0;
    for(ll i = 0; i < n; i++){
        now = i;
        if(s[i]=='#') break;
    }
    ll ans = 0;
    for(ll i = now+1; i < n; i++){
        if(s[i]=='.') ans++;
    }
    cout << min(n-now-ans, ans) << endl;
    return 0;
}