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)

function Main(input) {
    const N = parseInt(input[0])
    const S = input[1]
    
    var BW = [];
    if(S.charAt(0) == "."){
        BW.push(0);
    }

    var prev = S.charAt(0);
    var count = 0;
    for (let i = 0; i < N; i++) {
        const element = S.charAt(i);
        if(element == prev){
            count++
        } else {
            BW.push(count);
            prev = element;
            count = 1;
        }
    }
    if(count > 0) {
        BW.push(count);
    }
    if(BW.length %2 > 0){
        BW.push(0);
    }


    var min = Number.MAX_SAFE_INTEGER;

    for (let i = 0; i < BW.length/2 + 1; i++) {
        var sum = 0;
        for (let j = 0; j < BW.length/2; j++) {
            sum += i <= j ? BW[j*2] : BW[j*2+1];
        }
        
        min = Math.min(sum, min);
    }

    console.log(min);
    
}

// 改行・空白で分割
Main(require("fs").readFileSync("/dev/stdin", "utf8").trim().split(/\n|\s/));