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<string.h>
#include<math.h>

int main()
{
	int N;
	char s[200001];
	int i;
	int j = 1;
	int ans =200001;
	int pos[2][200001] ;
	int w = 0,b = 0;
	printf("yes");
	scanf("%d", &N);
	scanf("%s", s);
	s[N] = '#';
	for (i = 0;i < N;i++)
	{
		if (s[i] == '#')b++;
		else w++;
		if (s[i] == '.'&&s[i + 1] == '#')
		{
			pos[0][j] = w;//'.'の総和
			pos[1][j] = b;//'#'の総和
			j++;
		}
	}

	int okikae = 0;
	for (i = 1;i < j;i++)
	{
		okikae = pos[1][i] + (pos[0][j]-pos[0][i]);//wa_b[pos[i]] + (w- wa_w[pos[i]]);
		if (ans > okikae)ans = okikae;
	}
	printf("%d\n", ans);
	return 0;
}