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) {
    "use strict";
    const elements = input.split('\n');
    let blackFlag = false;
    let numBlack = 0;
    let numWhiteAfterBlack = 0;

    for (let i = 0; i < elements[0]; i++) {
        if (blackFlag === false && elements[1][i] === '#') {
            blackFlag = true;
        }
        if (blackFlag === true && elements[1][i] === '.') {
            numWhiteAfterBlack++;
        }
        if (elements[1][i] === '#') {
            numBlack++;
        }
    }

    if (numWhiteAfterBlack === 0) {
        console.log('0');
    } else if (numBlack <= numWhiteAfterBlack) {
        console.log(numBlack);
    } else {
        console.log(numWhiteAfterBlack);
    }
}

Main(require('fs').readFileSync('/dev/stdin', 'utf-8'));