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<stdio.h>
#include<iostream>
#include<string.h>
#include<string>
#include<queue>
#include<utility>
#include<vector>
#include<map>
#include<functional>
#include<math.h>
#include<algorithm>
typedef long long ll;
using namespace std;

int main(){
  int N;
  string s;
  cin >> N >> s;
  if(s.length()==1){
    cout << "0" << endl;
    return 0;
  }
  int ans = 0;
  for(int i=0;i<s.length()-1;i++){
    char niko = s[i];
    char ikko = s[i+1];
    if(niko == ikko){
      s[i+1] = (s[i+1]== '.' ? '#' : '.');
      ans++;
    }
  }
  cout << ans << endl;
  return 0;
}