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 i,j,n,a=0,b=0,sum=0;
  char str[200000]={0};
  int juge[200000]={0};
  scanf("%d",&n);
  scanf("%s",str);
 
  for(i=0;i<n;i++){
  	if(str[i]=='.'){
      a++;
      juge[i]=1;
    }
    else{
     b++;
      juge[i]=0;
    }
  }
  if(b>a){
  for(i=0;i<n;i++){
  if(juge[i]<juge[i+1]){
    juge[i+1]=0;
    sum++;
  }
  }
  }
  if(b<a){
  for(i=0;i<n;i++){
  if(juge[i]<juge[i+1]){
    juge[i+1]=1;
    sum++;
  }
  }
  }
  
  printf("%d",sum);
  return 0;
}