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;
  int a,kosu=0,bl=0,wh=0;
  char Su[200000];
  
  scanf("%d",&N);
  scanf("%s",Su);
  
  for(a=0;a<N;a++){
    if(Su[a]=='#'){
      bl++;
    }else{
      wh++;
    }
  }
  if(bl>=wh){
    for(a=0;a<N;a++){
      if(Su[a] == '#' && Su[a+1] == '.'){
        Su[a+1] = '#';
        kosu++;
      }
    }
  }else{
    for(a=0;a<N;a++){
      if(Su[a] == '#' && Su[a+1] == '.'){
        Su[a] = '.';
        kosu++;
      }
    }
  }
  
  printf("%d",kosu);
  
  return 0;
}