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(){
  int N,cnt=0,i,min;
  scanf("%d",&N);
  char S[N+1];
  scanf("%s",S);
  
  for(i=0;i<N;i++){
    if(S[i]=='.')cnt++;
  }
  if(S[0]=='.'){
    cnt--; 
    min=cnt;
  }
  else {
    min=cnt; 
    cnt++;
  }

  for(i=1;i<N;i++){
    if(S[i]=='.')cnt--;
    else cnt++;
    if(cnt<min){
      min=cnt;
    }
  }
  printf("%d\n",min);
}