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 Ruby (2.3.3) (judge verdict: Wrong Answer)


n = gets.chomp.to_i
 
s = gets.chomp
 
boundaries = []
curr = ""

before = 0

min = 9999999999

front_sum = 0
back_all = s.count(".")


s.chars.each_with_index do |a,i|
 
  if(a != curr)
    
    boundaries.push(i) if a == "#"
    curr = a
  
  end
 
end
 
 
if (boundaries.length == 0 || boundaries.length == 1)
  min = 0
end
 

boundaries.each do |i|

  
 front = s.slice(before, i)
   
 front_sum += front.count("#")
 back_sum = back_all - (i - front_sum)
# p "i: #{i}"
# p "i-front_sum: #{i - front_sum}"

# p "front_sum: #{front_sum}"
# p "back_sum: #{back_sum}"

 sum = front_sum + back_sum
 
 min = sum if(min > sum)

end

puts min