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 n int
	var s string

	fmt.Scanf("%d", &n)
	fmt.Scanf("%s", &s)

	if n <= 1 {
		fmt.Println(0)
		return
	}

	start := 0
	end := n
	if s[0:2] == ".#" {
		start++
	}
	if s[n-2:n] == ".#" {
		end--
	}

	iSharp := 0
	iDot := 0
	sharpByte := "#"[0]

	for i := start; i < end; i++ {
		if s[i] == sharpByte {
			iSharp++
		} else {
			iDot++
		}
	}

	if iSharp < iDot {
		fmt.Println(iSharp)
	} else {
		fmt.Println(iDot)
	}
}