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<algorithm>
#include<climits>
#include<cmath>
#include<cstdlib>
#include<iomanip>
#include<iostream>
#include<numeric>
#include<string>
using namespace std;
 
long gcd(long x, long y) { if (x > y) { return gcd(y, x); } long r; while (y != 0) { r = x % y; x = y; y = r; }return x; }
long lcm(long x, long y) { return(x / gcd(x, y)) * y; }
void indexsort(long* first, long* last, long* func) { sort(first, last, [&](long a, long b) {return func[a] < func[b]; }); }
//--------------------
 
int main() {
 
	long N; cin >> N;
	string S; cin >> S;
	long mycount = 0;
	long hidari = 0;
    long migi = 0;
	for (int i = 0; i <= N - 1; i++) if (S[i] == '.') hidari++; else break;
    for (int i = 0; i <= N - 1; i++) if (S[N - i - 1] == '#') migi++; else break;
	for (int i = hidari; i <= N - 1 - migi; i++) if (S[i] == '#') mycount++;
 
	cout << min(mycount, N - hidari - migi - mycount) << endl;
 
}