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<vector>
#include<string>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<tuple>
#include<iomanip>
#include<map>
#include<queue>
#include<set>
#define int long long
using namespace std;
const int INF = 1e10;
const int ZERO = 0;

signed main() {
	int N;
	string S;
	cin >> N >> S;
	int ret = 0;
	for(int i = N - 1;i >= 1;i--) {
		if(S.at(i) == '.' && S.at(i - 1) == '#') {
			S.at(i) = '#';
			ret++;
		}
	}
	cout << ret << endl;
}