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: Runtime Error)

#include<stdio.h>

int main()
{
  int n, i, flag_s, flag_l, b_sum=0, w_sum=0;
  scanf("%d", &n);
  char s[n];
  scanf("%s", s);

  for(i=0;i<n;i++){
    if(s[i]=='#'){
      flag_s = i;
      break;
    }
  }

  for(i=n-1;i>=0;i--){
    if(s[i]=='.'){
      flag_l = i;
      break;
    }
  }

  for(i=flag_s;i<flag_l;i++){
    if(s[i]=='#'){
      b_sum++;
    }
  }
  for(i=flag_s;i<flag_l;i++){
    if(s[i]=='.'){
      w_sum++;
    }
  }

  if(b_sum>=w_sum){
    printf("%d\n", w_sum);
  }
  else{
    printf("%d\n", b_sum);
  }
  return 0;
}