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: Runtime Error)

#include<bits/stdc++.h>
#define REP(i,n) for(int i=0;i<(n);++i)
#define ALL(v) (v).begin(),(v).end()
#define INF 1e9
#define MOD 1e9+7
typedef long long llong;
using namespace std;

int main(){
	int n;
	vector<char> s(n);
	cin>>n;
	REP(i,n){
		cin>>s[i];
	}
	
	int sum=0;//w.
	int summ=0;//b.
	int cnt=0;
	int j;
	for(j=n-1;j>=0;--j){
		if(s[j]!='#'){
			cnt++;
			break;
		}
	}
	for(int i=j-1;i>=0;--i){
		if(s[i]=='.') cnt++;
		else{
			summ++;
			sum+=cnt;
			cnt=0;
		}
	}
	
	//cout<<sum<<' '<<summ<<endl;
	cout<<min(sum,summ)<<endl;
}