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(void){
  int n,i,j;
  char s[200000];
  char a='.';
  char b='#';
  int cnt=0;
  int acount=0;
  int bcount=0;
  
  scanf("%d", &n);
  scanf("%s", s);
  
  for(j=0;j<n;j++){
    if(s[j]==a){
      acount++;
    }
    if(s[j]==b){
      bcount++;
    }
  }
  
  for(i=0;i<n;i++){
    if(s[i]!=s[i+1]){
        if(acount<=bcount){
         if(s[i]==a){
           cnt++;
           s[i]=b;
         }
       }
      else{
          if(s[i]==b){
           cnt++;
           s[i]=a;
          }
       }
      
    }
  }
  printf("%d\n", cnt);
  return 0;
}