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) {
    const args = input.split('\n');

    const N = parseInt(args[0]);
    const stones = args[1].split('');

    let cam_count = 0;
    let sya_count = 0;

    let isNotcou = true;

    for(let i = 0; i < N; i++) {
        if (isNotcou) {
            if (stones[i] == '#') {
                isNotcou = !isNotcou;
            }
        } else {
            if (stones[i] == '.') {
                cam_count++;
            } else if (stones[i] == '#') {
                sya_count++;
            }
        }
    }

    const ans = cam_count < sya_count ? cam_count : sya_count;

    console.log(ans);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));