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<string>
#include <vector>
using namespace std;

typedef  long long ll;

int main(){
	
	int N;
  	string S;
  	cin >> N;
  	cin >> S;
	int flag=0;
  	int contb=0;
  	int contw=0;
  	int black=0;
   	int white=0;
  	for(int i = 0; i < N ;i++){
    	if(S[i]=='.'){
        	white++;
        }else{
        	black++;
        }  
    }
  
  	

	  	for(int i = 0; i < N ; i++){
    		if(S[i]=='#'&&flag ==0){
				flag = 1;
	    
	    	}else if(S[i]=='.'&&flag ==1){
    	     	contw++;
        	}
    	}
      

      //cout << black <<cont<<endl;
      for(int i = N; i >= 0 ; i--){
    		if(S[i]=='#'){
				contb++;
	    		//cout << i << S[i];
	    	}else if(S[i]=='.'){
    	     	break;
        	}
    	}
        
        
        //cout << black <<cont<<endl;
    
    	contb = black-contb;
    
    

	if(contb>contw)cout << contw<<endl;
	else cout << contb<<endl;
  
}