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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

int
main(int argc, char *argv[])
{
  int n; char s[400000] = {}; int k = -1; int b[400000];
  scanf("%d%s", &n, s); int j = 0;
  for(int i = 0; i < n; i++){
    if(s[i] == '#'){
      b[j] = i;
      j++;
    }
  }

  int black = j;
  int m = 400000;
  if(j != 0){
  for(int i = 0; i <= black; i++){
    if(i + n - black - (b[i] - i) < m){
      m = i + n - black - (b[i] - i);
    }
  }
  }
  else{
    m = 0;
  }

  printf("%d\n", m);
  return 0;
}