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>
#include <stdlib.h>

int count_black(int n,char s[n],int i){
    int j=i+1;
    while(s[j]=='#' || j==n-1){
        j=j+1;
    }
    return j-i;
}

int count_white(int n,char s[n],int i){
    int j=i-1;
    while(s[j]=='.' || j==n-1){
        j=j-1;
    }
    return i-j;
}

int main(void)
{
    int n,ans=0,i,bl,wh;
    scanf("%d",&n);
    char s[n];
    scanf("%s",&s);
    for(i=0; i<n-1; i++){
        if(s[i]=='#' && s[i+1]=='.'){
            bl=count_black(n,s,i);
            wh=count_white(n,s,i+1);
            if(bl>wh){
                ans=ans+wh;
            }else{
                ans=ans+bl;
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}