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;
  char stone[1000000]={};
  scanf(" %d",&n);
  scanf(" %s",stone);

  int i=0;
  int ans=0;
  int ans2=0;


  int ch=0;
  for (i = 0; ; i++) {
    if(stone[i]=='#'){ans+=ch;}
    else ch++;
    if(stone[i]=='\0')break;
  }

  ch=0;

  for (i = 0; ; i++) {
    if(stone[i]=='.'){ans2+=ch;}
    else ch++;
    if(stone[i]=='\0')break;
  }
  if(ans>ans2)printf("%d\n",ans2);
  else printf("%d\n",ans);

return 0;
}