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: Accepted)

#include <stdio.h>
int main(void){
  int i,n;
  scanf("%d",&n);
  int x=n;
  char s[n];
  int ss[n+1];
  int sss[n+1];
  scanf("%s",s);
  ss[0]=0;
  sss[0]=0;

  for(i=0;i<n;i++){
    if(s[i]=='#'){
      ss[i+1]=ss[i]+1;
      sss[i+1]=sss[i];
    }else{
      ss[i+1]=ss[i];
      sss[i+1]=sss[i]+1;
    }
  }
  

  for(i=0;i<=n;i++){
    if(x>ss[i]+sss[n]-sss[i]){
      x=ss[i]+sss[n]-sss[i];
    }
  }

  printf("%d",x);

  
  return 0;
  
}