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: Runtime Error)

'use strict'
function Main(input){
  input=input.split(/\n/);
  var N=input.shift()-0;
  var S=input.join('').trim().replace(/\s+/,'').split('');
  var B=0,W=0;
  for(let i=0;i<N;i++){
    if(S[i]==='.'){
      W++;
    }else{
      B++;
    }
  }
  var a=[W];
  for(let i=0;i<N;i++){
    let d=(S[i]==='.'?-1:1);
    a.push(a[i]+d);
  }
  var ans=Math.min.apply(null,a);
  console.log(ans);
}

Main(require('fs').readFileSync('/dev/stdin','utf8'));