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>
#define rep(i, n) for (ll i = 0; i < (int)(n); i++)
#define repR(i, n) for(ll i = n; i >= 0; i--)
#define For(i, m, n) for(ll i = m; i < n; i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;
typedef long double ld;
using namespace std;
struct Fast {Fast(){std::cin.tie(0);std::ios::sync_with_stdio(false);}} fast;

int main(void){
    ll result = 0;
    ll N;
    string S;
    cin >> N >> S;
    
    ll x = 0, y = 0;
    bool flag = false;
    rep(i, S.size()){
        if(S[i] == '#'){
            if(flag){
                if(x < y){
                    result += x;
                }else{
                    result += y;
                }
                x = 0;
                y = 0;
                flag = false;
            }
            x ++;
        }else{
            y ++;
            flag = true;
        }
    }
    
    if(flag){
        if(x < y){
            result += x;
        }else{
            result += y;
        }
    }
    
    cout << result << endl;
    return 0;
}