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;

using ll = long long;
const ll amari = 1e9+7;
#define ben(a) a.begin(),a.end()
#define pb(a,b) a.push_back(b)

int main(){
	int n;
	string s;
	cin >> n >> s;
	int b = 0;
	int w = 0;
	for(int i = n; i >= 0; i--){
		if(s[i] != '#')n = i;
	}
	int k = 0;
	for(int i = 0; i < n; i++){
		if(s[i] != '.')k = i;
	}
	for(int i = k; i <= n; i++){
		if(s[i] == '.')w++;
		else b++;
	}
	cout << min(b,w) << endl;
	return 0;
}
//g++ AtCoder.cpp