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) {
	inputs = input.split("\n")
    var a = parseInt(inputs[0])
    var b = inputs[1].split("")
    //右から白を消して行くver
    var left_white_count = 0
    var flag = true
    if(b[0] == "."){
        flag = true
        b.forEach(function(str){
            if(flag){
                if(str == "."){
                    left_white_count += -1
                }else{
                    flag = false
                }
            }
        })
    }
    // console.log(left_white_count)
    b.forEach(function(str){
        if(str == "."){
            left_white_count += 1
        }
    })
    //左から黒を消して行くver
    var right_black_count = 0
    if(b.slice(-1)[0] == "#"){
        flag = true
        b.reverse().forEach(function(str){
            if(flag){
                if(str == "#"){
                    right_black_count += -1
                }else{
                    flag = false
                }
            }
        })
    }
    // console.log(right_black_count)
    b.forEach(function(str){
        if(str == "#"){
            right_black_count += 1
        }
    })
    if(right_black_count >= left_white_count){
        console.log(left_white_count)
    }else{
        console.log(right_black_count)
    }
}

//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));