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)

function Main(input) {
  input = input.split("\n");
  var N = parseInt(input[0].split(" ")[0]);
  var S = input[1].split(" ")[0];

  var count_All_white = S.split("#").length-1;

  var count_dot=0;
  for(var i=0; i < S.length; i++){
    if(S[i] == "#") break;
    count_dot++;
  }

  var count_sharp = S.length-1;
  for(var i=S.length-1; i == 0; i--){
    if(S[i] == ".") break;
    count_sharp--;
  }

  var sharp_num=0;
  var dot_num=0;
  for(var i=count_dot;i<count_sharp+1;i++){
    if(S[i] == "#") sharp_num++;
    if(S[i] == ".") dot_num++;
  }

  console.log(Math.min(count_All_white,sharp_num, dot_num));
}

var input=Main(require("fs").readFileSync("/dev/stdin", "utf8"));
// var input=`3
// #.#`
// Main(input);