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) {
  var args = input.split('\n');
  var n = parseInt(args.shift());
  var s = args.shift();
  var bCount = 0;
  var wCount = 0;
  for(var sc of s) {
    if (!bCount && sc === '.') {
      continue;
    }
    if (sc === '#') {
      bCount++;
      continue;
    }
    wCount++;
  }
  console.log(wCount < bCount ? wCount : bCount);
}

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