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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

// inputに入力データ全体が入る
function Main(input) {
	// 1行目がinput[0], 2行目がinput[1], …に入る
  input = input.split("\n")
  tmp0 = input[0].split(" ")
  N = Number(input[0])
  S = input[1]

  ans0 = 0
  before = S[0]
  for(var i=1; i < N; i++)
  {
    if(before === '#' && S[i] === '.')
    {
      ans0++
      before='#'
      continue
    }
    before=S[i]
  }

  ans1=0
  for(var i=1; i < N; i++)
  {
    if(S[i] === '#')
    {
      ans1++
      continue
    }
  }

  if(ans0 < ans1){
    console.log(ans0)
  }else{
    console.log(ans1)
  }
}
//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
// Main("6\n###.#.\n")