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 <stdint.h>
#include <inttypes.h>
#include <stdlib.h>

#define SIZE (2*10*10*10*10*10)
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))

char S[SIZE];

int main()
{
  int N;
  int cnt = 1;
  int i;
  int result = 0;
  int btotal = 0;
  int bpre = 0;
  int bpost = 0;
  int wtotal = 0;
  int wpre = 0;
  int wpost = 0;
  int b1st = -1;
  int bend = -1;
  int wend = -1;
  int isw = 0;
  char dummy;

  cnt = scanf("%d", &N);
  cnt = scanf("%*c", &dummy);
  
  i=0;
  cnt = 1;
  while (cnt == 1) {
    cnt = scanf("%c", &S[i]);

//    printf("%d: %d: %c\n", N, i, S[i]);
    
    if (cnt != 1) break;

    if ((S[i] != '.') && (S[i] != '#')) break;
    if (i == N) break;
    if (S[i] == '.') {
      wtotal++;
      wend = i;
      if (b1st == -1) {
        wpre++;
      } else {
        wpost++;
      }
    } else {
      btotal++;
      bend = i;
      if (b1st == -1) {
        b1st = i;
      } else {
        bpost++;
      }
    }
    i++;
  }

  if (b1st == -1) {
    printf("0");
    return 0;
  }

  if (bend > wend) {
    bpost -= (bend - wend);
    if (bpost == 0) {
      printf("0");
      return 0;
    }
  }

  if ((wpost) >= (bpost + 1)) {
    result = bpost + 1;
  } else {
    result = wpost;
  }
    
  printf("%d", result);

  return 0;
}