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 <string.h>

int main(int argc, char const *argv[])
{
    int count;
    char stone[200000];
    char stone_b[200000];
    int ans=0,ans_b;

    scanf("%d",&count);
    scanf("%s",stone);

    memcpy(stone_b,stone,sizeof(char)*count);

    for(int i = 1; i < count; i++)
    {
        if(stone[i-1]=='#'&&stone[i]=='.') {
            ans++;
            stone[i]='#';
        }
    }

    for(int i = 0; i < count-1; i++)
    {
        if(stone[i]=='#'&&stone[i+1]=='.'){
            ans_b++;
            stone[i]='.';
        }
    }
    
    printf("%d\n",(ans<ans_b)?ans:ans_b);
    
}