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 <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main(){
    int n;
    string s;
    cin >> n >> s;
    int dot = 0;
    while(dot < n && s[dot] == '.') dot++;

    int sh = s.size();
    while(sh >= 0 && s[sh-1] == '#') sh--;

    if(sh == 0){
        cout << 0 << endl;
        return 0;
    }

    if(dot == n-1){
        cout << 0 << endl;
        return 0;
    }
    int ans1 = 0;
    int ans2 = 0;

    for(int i=dot; i<n; i++){
        if(s[i] == '#') ans1++;
        else ans2++;
    }
    ans1 -= (n - sh);
    cout << min(ans1, ans2) << endl;
    return 0;
}