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)

"use strict";

function Main(input) {
  input = input.split("\n");
  var N = parseInt(input[0], 10);
  var S = input[1];
  var s = [...S];
  var firstB = s.indexOf("#");
  var toB = 0;

  if (firstB >= 0) {
    for (var i = firstB; i < N; i++) {
      if (s[i] != "#") {
        toB++;
      }
    }
  }

  var lastW = s.lastIndexOf(".");
  var toW = 0;

  if (lastW >= 0) {
    for (var _i = 0; _i < lastW; _i++) {
      if (s[_i] != ".") {
        toW++;
      }
    }
  }

  var blackNum = 0;

  for (var _i2 = 0; _i2 < N; _i2++) {
    if (s[_i2] == "#") {
      blackNum++;
    }
  }

  console.log(Math.min(blackNum, toW, toB));
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));