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 Julia (0.5.0) (judge verdict: Time Limit Exceeded)

readline_() = readline() |> chomp
# a b c d e -> Array{SubString{String},1}
readline_array_string() = readline() |> chomp |> split
# 1 2 3 4 5 -> Array{Int64, 1}
readline_array_int() = [parse(Int, x) for x in readline() |> chomp |> split]
read_int() = parse(Int, readline() |> chomp)

function omit(str)
    count = 0
    l = length(str)
    ind = Int[]
    i = 1
    while i <= l-1
        if str[i:i+1] == "#."
            count += 1
            i += 2
        else
            push!(ind, i)
            i += 1
        end
    end

    if l >= 2
        if str[l-1:l] != "#."
            push!(ind, l)
        end
    end

    if count == 0
        return 0
    else
        count += omit(str[ind])
    end
    return count
end

n = read_int()
str = readline_()
value = omit(str)
print(value)