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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
        "fmt"
)

func main() {
        var s, b, w []int
        var n int

        fmt.Scanf("%d", &n)
        var nb, nw int
        for i := 0; i < n; i++ {
                var c rune
                fmt.Scanf("%c", &c)
                if c == '.' {
                        s = append(s, 0)
                        nw++
                } else {
                        s = append(s, 1)
                        nb++
                }
                b = append(b, nb)
                w = append(w, nw)
        }

        var idx, last int
        last = s[0]

        for i := 1; i < n; i++ {
                if last == 1 && s[i] == 0 {
                        idx = i
                        break
                }
                last = s[i]
        }

        lb := b[idx]
        rw := w[n-1] - w[idx]

        var m int
        m = lb + rw
        if m > b[n-1] {
                m = b[n-1]
        }
        if m > w[n-1] {
                m = w[n-1]
        }

        fmt.Println(m)
        /**
        fmt.Println(s)
        fmt.Println(b)
        fmt.Println(w)
  **/
}