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 <vector>
#include <string.h>
#include <algorithm>
using namespace std;
int main(void){
int N;
cin>>N;
char str[N+1];
cin>>str;
vector<int> v;
int count=0;
for(int i=0;i<N;i++){
    if(str[i]==str[i+1]){count++;}
    else {if(count!=0)v.push_back(count+1); if(count==0)v.push_back(1); count=0;}
}
v.push_back(count);
int count1=0; int count2=0;
for(int i=0;i<v.size()-2;i++){
   if(i%2==0){count1+=v[i];}
   if(i%2==1){count2+=v[i];}
}
int ans=min(count1,count2);
cout<<ans;
return 0;
}