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 <cmath>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <iomanip>
#include <map>
#include <stack>
#include <queue>

using namespace std;

typedef long long ll;


int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll n;
    string s;
    cin>>n;
    cin>>s;
    string t=s;
    ll ans1=0,ans2=0;
    for (ll i=0; i<n-1; i++){
        if(t[i]=='#'&&t[i+1]=='.') {
            t[i+1]='#';
            ans1++;
        }
    }
    for (ll i=0; i<n-1; i++){
        if(s[i]=='#'&&s[i+1]=='.') {
            s[i]='.';
            ans2++;
        }
    }
    cout<<min(ans1,ans2)<<endl;
}