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: Accepted)

#include<stdio.h>
 
int main()
{
	int n,b = 0,w = 0,i;
	scanf("%d",&n);
  
  	char c[n];
	scanf("%s",c);
	
	for(i = 0;i < n;i++){
		if(c[i] == '.') w++;
	}
	
	int min = w;
  
	for(i = 0;i < n;i++){
		if(c[i] == '#') b++;
		else w--;
		if(b + w < min) min = b + w;
	}
	printf("%d",min);
	return 0;
}