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<cmath>
#include<algorithm>
#include<string>
using namespace std;
int main(){
  int n;cin>>n;
  string s;cin>>s;
  int i;

  int count=0;
  int tmp=n;
  for(i=n-1;i>=0;i--){
    if(s[i]=='#') tmp--;
    else break;
  }

  int a=0;
  for(i=0;i<n;i++){
    if(s[i]=='.') a++;
    else break;
  }


  for(i=a;i<tmp;i++){
    if(s[i]=='#') count++;
  }

  int b=n;
  b-=a;
  b-=n-tmp;

  if(b<count*2) count=b-count;

  cout<<count<<endl;

}