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>
#include <stdlib.h>
#include <string.h>

#define _max(_x, _y) ((_x)>(_y)?(_x):(_y))
#define _min(_x, _y) ((_x)>(_y)?(_y):(_x))

int main(void)
{
  int N, index, flg, count_dot, count_sharp;
  char S[200000];
  scanf("%d %s", &N, &S);
  //printf("N(%d) S(%s)\n", N, S);
  flg = 0;
  count_dot = 0;
  for (index = 0; index < N; ++index) {
    if (flg == 1 && S[index] == '.') {
      count_dot++;
      continue;
    }
    if (S[index] == '#') {
      flg = 1;
    }
  }
  
  flg = 0;
  count_sharp = 0;
  for (index = N-1; index >= 0; --index) {
    if (flg == 1 && S[index] == '#') {
      count_sharp++;
      continue;
    }
    if (S[index] == '.') {
      flg = 1;
    }
  }
  
  printf("%d\n", _min(count_dot, count_sharp));
  return 0;
}