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 n;
  int white = 0, black = 0;
  char s[200000];
  scanf("%d",&n);
  (void) getchar();
  scanf("%s",s);
  for ( int i = 0; i < n; i++ ) {
    if ( s[i] == '#' ) {
      white++;
    } else {
      black++;
    }
  }

  if ( white < black ) {
    printf("%d\n",white);
  } else if ( white == black ) {
    if ( s[0] == '.' ) {
      printf("%d\n",black-1);
    } else if ( s[n-1] == '#' ) {
      printf("%d\n",white-1);
    } else {
      printf("%d\n",black);
    }
  } else {
    printf("%d\n",black);
  }
  return 0;
}