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>
using namespace std;

int main(){
    int n;
    string s;
    cin >> n >> s;
    int b = 0, w = 0;
    for(int i = 0; i < n; i++){
        if(s[i] == '.') w++;
        else            b++;
    }
    if(w == 0 || b == 0){
        cout << 0 << endl;
        return 0;
    }
    int ans = n, wtmp = 0, btmp = 0;
    for(int i = 0; i < n; i++){
        if(s[i] == '.'){
            wtmp++; w--;
        }else{
            btmp++; b--;
        }
        ans = min(ans, btmp+w);
    }
    cout << ans << endl;
    return 0;
}