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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <cstdio>
#include <iostream>
#include <algorithm>

#define WHITE '.'
#define BLACK '#'

using namespace std;

int main() {
	int white = 0, black = 0;
	bool white_flag = false, black_flag = false;

	int n;
	char c;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> c;
		if (c == WHITE) {
			if (!black_flag) {
				black_flag = true;
			}
			if (white_flag) {
				white++;
			}
		}
		else {
			if (!white_flag) {
				white_flag = true;
			}
			if (black_flag) {
				black++;
			}
		}
	}
	int ans = 0;
	white <= black ? ans = white : ans = black;
	cout <<  ans << endl;
}