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(){

  int N; cin >> N;
  string S; cin >> S;

  int tmp0 = 0;
  int tmp1 = 0;
  // bool flag0 = false;
  // bool flag1 = false;
  int time = 0;

  bool flag0 = true;

  for(int i = 0 ; i < N ; ++i){

    if(S[i] == '#' && S[i-1] == '.'){
      time += min(tmp0, tmp1);
      tmp0 = 0; tmp1 = 0;
      flag0 = false;
    }

    if(S[i] == '#') tmp0++;
    if(S[i] == '.') tmp1++;
    // cout << tmp0 << "\t" << tmp1 << endl;

    if(i == N-1){
      time += min(tmp0, tmp1);
    }

    if(i == N-1 && S[i] == '.'){
      // cout << tmp0 << "\t" << tmp1 << endl;
      if(tmp0 > tmp1) continue;
      time -= tmp0;
      time += tmp1;

    }

    if(i == N-1 && flag0 == true && S[0] == '.'){
      time -= tmp1;
    }

  }
    

  cout << time << endl;
  


}