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;
using ll = long long;

//container util
#define SORT(c) sort((c).begin(),(c).end())

//repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//print
#define pv(val) cerr << #val << '=' << (val) << endl

const int INF = 1e9;

int main(void){

	int N; cin >> N;
	string S; cin >> S;

	bool black = false;
	int ans;
	int cnt = 0;
	REP(i,N){
		if(S[i] == '#' and !black) black = true;
		else if(black and S[i] == '.') cnt++;
	}
	ans = cnt;

	bool white = false;
	cnt = 0;
	for(int i=N-1;i>=0;--i){
		if(S[i] == '.' and !white) white = true;
		else if(white and S[i] == '#') cnt++;
	}
	ans = min(ans, cnt);
	cout << ans << endl;
	return 0;

}