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 <math.h>
#include <string.h>
#include <ctype.h>

int main(void) {
      int n, count = 0, spos = 0, memo = 0;
      char s[4000002];

      if(scanf("%d %s", &n, s) == 1);

      while(n > 0 && s[n - 1] == '#') {
            n--;
      }

      while(spos < n && s[spos] == '.') {
            spos++;
      }

      memo = n - spos;

      for(int i = spos; i < n; i++) {
            if(s[i] == '#') {
                 count++;
            }
      }

      if(memo / 2 >= count) {
            count = 0;
            for(int i = n - 1; i >= spos; i--) {
                  if(s[i] == '#') {
                        count++;
                  }
            }
      } else {
            count = 0;
            for(int i = n - 1; i > spos; i--) {
                  if(s[i] == '.') {
                        count++;
                  }
            }
      }

      printf("%d", count);

      return 0;
}