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()
{
	string S;
	unsigned int N, answer;
	cin >> N >> S;
	unsigned int count_sharp, count_dot;
	count_sharp=0;
	count_dot=0;
	unsigned int sharp_dot_location_left;
	unsigned int sharp_dot_location_right;
	for (int i=0;i<N-1;i++){
		if (S.at(i)=='#' && S.at(i+1)=='.'){
			sharp_dot_location_left =i;
			break;
		}	
	}
	for (int i=N-1;i>0;i--){
		if (S.at(i-1)=='#' && S.at(i)=='.'){
			sharp_dot_location_right =i;
			break;
		}	
	}
	for (int i=sharp_dot_location_right;i>=0;i--){
		if (S.at(i)=='#') count_sharp ++;
	}
	for (int i=sharp_dot_location_left;i<N;i++){
		if (S.at(i)=='.') count_dot ++;
	}
	if (count_sharp > count_dot){
		answer = count_dot;
	}
	else{
		answer = count_sharp;
	}
	cout << answer << endl;

	return 0;
}