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>
using namespace std;

int main(void){
    int n, num_b, num_w, first_pointer;
    string s;

    cin >> n >> s;


    first_pointer = n+1;
    for(int i = 0;i < n-1;i++){
        if(s[i] == '#'){
            first_pointer = i;
            break;
        } 
    }

    num_b = 0;
    num_w = 0;

    for(int i = first_pointer;i < n;i++){
        if(s[i] == '#')     num_b++;
        else                num_w++;
    }

    if(num_b > num_w)   cout << num_w << endl;
    else                cout << num_b << endl;

    return 0;
}