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: Time Limit Exceeded)

#include <bits/stdc++.h>
using namespace std;

int main(void){
  int N;
  string S;
  cin >> N >> S;
  int cntMin = INT_MAX;
  for (int border = 0; border <= N; border++) {
    int cnt = 0;
    for (int i = 0; i < N; i++) {
      if (i < border) {
        if (S[i] == '#') { cnt++; }
      } else {
        if (S[i] == '.') { cnt++; }
      }
    }
    if (cntMin > cnt) { cntMin = cnt; }
  }
  cout << cntMin;
}