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>
#include <math.h>

int main(){
    int min(int a, int b);
    int n,i;
    int dot_r=-1,sharp_r=-1;
    int dot_n_r=0,sharp_n_r=0;
    int dot_n_l=0,sharp_n_l=0;
    char *s;

    scanf("%d", &n);
    s = malloc(sizeof(char)*(n+1));
    scanf("%s", s);

    for(i=n-1;i>=0;i--){
        if(s[i] == '#'){
            sharp_r = i;
            break;
        }else{
            dot_n_r++;
        }
    }
    if(sharp_r == -1){
        printf("0\n");
        return 0;
    }

    for(i=sharp_r;i>=0;i--){
        if(s[i] == '.'){
            dot_r = i;
            break;
        }else{
            sharp_n_r++;
        }
    }
    if(dot_r == -1){
        printf("%d\n",min(dot_n_r, sharp_n_r));
        return 0;
    }

    for(i=0;i<=dot_r;i++){
        if(s[i] == '.'){
            dot_n_l++;
        }else if(s[i] == '#'){
            sharp_n_l++;
        }
    }
    printf("%d\n",min(dot_n_l, sharp_n_l)+min(dot_n_r, sharp_n_r));


    return 0;

}

int min(int a, int b){
    if(a<b){
        return a;
    }else{
        return b;
    }
}