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: Accepted)

fun main(args: Array<String>) {
  val n = readLine()!!.toInt()
  val input = readLine()!!
  val count = IntArray(n + 1)
  for (i in 1..n) {
    if (input[i - 1] == '#') {
      count[i] = count[i - 1] + 1
    } else {
      count[i] = count[i - 1]
    }
  }
  val ans = (0..n).map {
    val cost1 = count[it]
    val cost2 = (n - it) - (count[n] - count[it])
    cost1 + cost2 }
      .min()
  println(ans)
}