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 <iomanip>
#include <vector>
#include <algorithm>
#include<string>

#define MAX 1000000000
#define MIN -10000000000

#define ll long long

using namespace std;
int main() {

    int n,i,j,k,tempb=0,tempw=0,switchh=0;
    ll ans=0;
    bool flg=false;
    cin>>n;
    string s;
    cin>>s;
    i=0;
    while(i<n){
        if(s[i]=='#')tempb++;
        else tempw++;

        if(i<n-1){
        if(s[i]!=s[i+1]){
            switchh++;
        }}else{
            switchh++;
        }
        if(switchh>=2){
            ans+=min(tempb,tempw);
            tempb=0;tempw=0;
            switchh=0;
        }
        i++;
    }

    if(ans==0)ans=min(tempb,tempw);
    cout << ans << endl;

    return 0;
}