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<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define mod 1000000007

int main(){
    int n;
    string s;

    cin>>n>>s;
    int a=0,b=0;
    bool flg=false;
    for(int i=0;i<n;i++){
        if(s[i]=='#'){
            flg=true;
        }
        if(flg && s[i]=='.') b++;
        if(flg && s[i]=='#') a++;
    }
    int cnt=0;
    if(s[n-1]=='#'){
        
        for(int i=n-1;i>=0;i--){
            if(s[i]=='.') break;
            cnt++;
        }
    }
    a-=cnt;
    if(a<0) a=0;
    cout<<min({a,b})<<endl;
}