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 <stdbool.h>
#include <string.h>

int main(void)
{
	int n, k;
	int num = 0, num2=0;
	char s[2 * 100000];
	bool is_b = false;

	scanf("%d", &n);
	scanf("%s", s);
	for (int i = 0; i < n; i++) {
		if (s[i] == '.') {
			if (is_b) num++;
			is_b = false;
		} else {
			is_b = true;
		}
	}

	for (int i = 0; i < n; i++) {
		if (s[i] != '.') {
			if (s[i+1] !='#') num2++;
		}
	}
	printf("%d", num < num2 ? num : num2);
	return 0;
}