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: Runtime Error)

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

int main(){
  long long count = 0,cou = 0,c = 0, N,a;
  string S;
  cin >> N >> S;
  for(long long i = 0; i < N; i++){
    if(S.at(i) == '#'){
      for(long long j = i; j < N; j++){
        if(S.at(j) == '.'){
          count++;
        }
        else{
          cou++;
        }
      }
      break;
    }
    if(S.at(N) == '#'){
      cou -= 1;
    }
  }
  c = N - cou;
  a= min(count,cou);
  a= min(a,c);
  cout << a;
}