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 PHP (5.6.30) (judge verdict: Wrong Answer)


<?php
fscanf(STDIN,"%d",$n);
fscanf(STDIN,"%s",$s);

$result=0;
//echo($S);
$count=0;
for($i = 0; $i < strlen($s); $i++) {
if($s[$i]=="#"){
  break;
}else{
  $count+=1;
}

}
//echo($count);

for($i = (strlen($s)-$count-1); $i >= 0; $i--) {
//echo($s[$i]);
if($s[$i]=="#"){

}else{
  $result+=1;
}

}


echo($result);
?>