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 <algorithm>
#include <map>
#include <set>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <random>
#include <chrono>
#include <queue>
#include <ctime>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
#define fs first
#define sc second
#define INF 1000000000
#define MOD 1000000007
#define EPS 0.00000001


int main() {
    int N; cin >> N;
    string S; cin >> S;
    
    bool b = false;
    int cntw = 0;
    for(int i=0; i<N; i++){
        if(S[i]=='#') b = true;
        if(b && S[i]=='.') cntw++;
    }
    
    bool w = false;
    int cntb = 0;
    for(int i=N-1; i>=0; i--){
        if(S[i]=='.') w = true;
        if(w && S[i]=='#') cntb++;
    }
    
    cout << min(cntb, cntw) << endl;
    
    
    
    return 0;
}