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: Accepted)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const ll MOD = 1000000007;
const ld PI = acos(-1);  
const ld EPS = 0.0000000001;


int main(){
    int n;
    string s;   cin >> n >> s;
    ll bc=0, wc=0;
    for(int i=0; i<s.size(); i++){
        if(s[i]=='#') bc += 1;
        else wc += 1;
    }
    ll ans=bc;
    bc = 0;
    for(int i=0; i<n; i++){
        ans = min(ans, bc+wc);
        if(s[i]=='#') bc += 1;
        else wc -= 1;
    }
    
 
    cout << ans << endl;
}