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);

  $shape = false;
  $count = 0;
  for ($i=0; $i<$n; $i++) {
    if (substr($s, $i, 1) == "#") {
        $shape = true;
    } 
    if (substr($s, $i, 1) == "." && $shape == true) {
        $count++;
    } 
}
if($shape == true &&  $count > 0) {
    $shapeC = substr_count($s, "#");
    $dotC = substr_count($s, ".");
    if($shapeC < $dotC){
        echo $shapeC;
    }else {
        echo $dotC;
    }
}else {
    echo "0";
}
  ?>