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 <string>
#include <utility>
#include <algorithm>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>

#define ll long long int
#define loop(v,n) for(ll v=0;v<n;v++)

using namespace std;

int main() {
    ll n;
    cin >> n;
    string s;
    cin >> s;
    int blk=0,wht=0,last=-1;
    loop(i,s.length()) {
        if(s[i]=='#') last=i;
        if(s[i]=='#') blk++;
        else wht++;
    }
    if(last == -1) {
        cout << 0 << endl;
        return 0;
    }
    if(s[s.length()-1] == '#') {
        int cur = s.length()-1;
        while(s[cur] == '#') {
            blk--;
            cur--;
        }
    }
    cout << min(blk,wht) << endl;
    return 0;
}