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 Kotlin (1.0.0) (judge verdict: Time Limit Exceeded)

fun main(args: Array<String>) {
    tenka12019beginnerc()
}

fun tenka12019beginnerc() {
    val n = readLine()!!.toInt()
    val s = readLine()!!

    var answer = Int.MAX_VALUE
    for (i in -1..s.lastIndex) {
        val count = s.slice(0..i).count { it == '#' } + s.slice(i + 1..s.lastIndex).count { it == '.' }
        answer = Math.min(answer, count)
    }

    println(answer)
}