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++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <iostream>
//#include <vector>
#include <string>
#include <algorithm>
//#include <math.h>
//#include <queue>
//#include <stack>
//#include <iomanip>

// sometimes used
//#include <set>
//#include <map>
//#include <numeric>
//#include <list>
//#include <deque>
//#include <unordered_map>

typedef long long LL;
//typedef long double LD;
using namespace std;
 
//#define MOD 1000000007
//#define MAX 100100
//#define NIL -1
//#define INFTY 1000000000000000000

int main(){
    LL n;
    string s;
    cin >> n;
    cin >> s;
    LL num_s=0;
    LL num_d=0;
    bool is_count_s=false;
    bool is_count_d=false;

    for(LL i=0; i<n; i++){
        if(is_count_s==true && s[i]=='.'){
            num_s++;
        }else if(s[i]=='#'){
            is_count_s=true;
        }
    }

    for(LL i=n-1; i>=0; i--){
        if(is_count_d==true && s[i]=='#'){
            num_d++;
        }else if(s[i]=='.'){
            is_count_d=true;
        }
    }

    LL ans=min(num_s, num_d);
    cout << ans << endl;

    return 0;
}