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>
// '.' is 白  '#' is black
int main(void) {
    int N; char S[200000];
    scanf("%d%s", &N, S);
    int cnt_white = 0;
    for (int i=0; i<N; i++) {
        if (S[i] == '#'){
            if (S[i+1] == '.'){
                S[i+1] == '#'; cnt_white ++;
            }
        }
    }
    int cnt_black = 0;
    for (int i=0; i<N; i++) {
        if (S[i] == '.') {
            if (S[i-1] == '#'){
                S[i-1] = '.'; cnt_black++;
            }
        }
    }
    if (cnt_black>cnt_white) {
        printf("%d\n", cnt_white);
    } else {
        printf("%d\n", cnt_black);
    }
}