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>
using namespace std;

int main() {
	int n,black= 0,sum,white=0,minv=200005;//blackは黒に、whiteは白にぬりかえるもの
	int j;
	cin >> n;
	string s;
	cin >> s;
	for (int i = 0; i < n; ++i) {
		if (s[i] == '.')++white;
		else ++black;
	}
	if (black == n || white == n)minv = 0;
	black = 0;
	for (int i = 0; i < n; ++i) {
		if (s[i] == '#') {
			++black;
		}
		else --white;
		sum = white + black;
		minv = min(sum, minv);
	}
	cout << minv << endl;
	return 0;
}