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;
int main() {
    int N;
    string s;
    cin >> N;
    cin >> s;
    int a = 0;
    int b = 0;
    int flag = 0;
    for(int i =0 ;i < N; i++) {
        if (s[i] == '.' && flag != 1) {
        } else {
            flag = 1;
        }
        if (flag == 1) {
            if (s[i] == '.') {
                a++;
            }else {
                b++;
            }
        }
    }
    if(a == N || b == N || a == 0 || b == 0){
        cout << '0' << endl;
    }else if(a <= b){
        cout << a << endl;
    }else{
        cout << b << endl;
    }
    return 0;
}