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<algorithm>
#include<cstring>
#include<cstdlib>

using namespace std;

int main() {
	int N;
	cin >> N;
	string S;
	cin >> S;

	int ans = N;
	int* white = new int[N];
	int* black = new int[N];
	white[0] = 0;
	black[0] = 0;
	if (S[0] == '.') { white[0] = 1; }
	else { black[0] = 1; }

	for (int i = 1; i < N; i++) {
		white[i] = white[i - 1];
		black[i] = black[i - 1];
		if (S[i] == '.') { white[i]++; }
		else { black[i]++; }
	}

	int change;
	for (int i = 0; i < N; i++) {
		change = white[N - 1] - white[i] + black[i] - black[0];
		if (ans > change) {
			ans = change;
		}
	}

	cout << ans << endl;

	delete[] white;
	delete[] black;
}