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 <ctype.h>
#include <string.h>
#include <math.h>
void print_int(int n)
{
    printf("%d\n",n);
}

void swap(int * a, int * b)
{
    int t = *a;
    *a = *b;
    *b = t;
}

void sort(int a[], int n)
{
    for(int i = 1; i < n; i++)
    {
        int j = i-1;
        while(j >= 0 && a[j+1] > a[j])
        {
            swap(&a[j+1],&a[j]);
            j--;
        }
        
    }
    
}

void print_list(int a[], int n)
{
    for(int i = 0; i < n; i++)
    {
        print_int(a[i]);
    }
    
}


char s[200000];
int main(void)
{
    int n;
    scanf("%d", &n);
    scanf("%s", s);
    int min = n;
    int temp = 0;
    //int flag = 0;
    int k = 0;
    int num = 0;
    int flag = -1;
    for(int i = 0; i < n; i++)
    {
        if(s[i] == '.')
            num++;
    }
    if(num == n)
    {
        print_int(0);
        return 0;
    }
    k = num;
    for(int i = 0; i < n; i++)
    {
        if(s[i] == '#')
        {
            if(flag == -1)
            {
                flag = -1;
            }
            //flag = 1;
            //k = 0;
            //s[i] = '.';
            k = k - (i - flag - 1);
            if(k + temp < min)
                min = k + temp;
            
            temp++;
            flag = i;
        }
    }
    if(flag == 0)
        min = 0;
    
    print_int(min);
    
    return 0;

}