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: Runtime Error)

#include<stdio.h>
int min2(int a, int b){return a>b?b:a;}
int n, now, min, i;
char s[200001];
int l[200001], r[200001];
int main(void){
  scanf("%d%s", &n, s);
  l[0]=(s[0]=='#');
  for(i=1; i<n; i++){
    l[i]=l[i-1]+(s[i]=='#');
  }
  r[n-1]=(s[n-1]=='.');
  for(i=n-2; i>=0; i++){
    r[i]=r[i+1]+(s[i]=='.');
  }
  min=n;
  for(i=0; i<n; i++){
    now=l[i]+r[i];
    min=min2(min, now);
  }
  printf("%d\n", min);
}