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>
#define min(x, y) ((x<y) ? (x) : (y))

int main(){
    int N;
    scanf("%d", &N);

    int ans = 0, i, j;
    char S[N];
    scanf("%s", &S);

    char kf=S[0];
    for (i=0; i<N; i++){
        if (kf == '#' && S[i+1] == '.'){
            ans++;
            kf = '#';
            continue;
        }else{
            kf = S[i];
        }
    }


    int ans2 = 0;
    kf = S[N-1];
    for (i=N-1; i>0; i--){
        if (kf == '.' && S[i-1] == '#'){
            ans2++;
            kf = '.';
            continue;
        }else{
            kf = S[i-1];
        }
    }

    printf("%d", min(ans, ans2));
 
    return 0;
}