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;
  scanf("%d%s", &n, s);
  for(int i = 0; i < n; i++){
    if(s[i] == '#'){
      k = i;
      break;
    }
    else if(i == n - 1){
      printf("%d\n", 0);
    }
  }

  int white = 0; int black = 0;

  if(k >= 0){
    for(int i = k + 1; i < n; i++){
      if(s[i] == '#'){
	black++;
      }
      else{
	white++;
      }
    }

    if(black + 1 < white){
      printf("%d\n", black + 1);
    }
    else{
      printf("%d\n", white);
    }
  }
  
  return 0;
}