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"
	"math"
)

func main() {
	var n int
	var s string
	fmt.Scan(&n, &s)

	preBlacked := false
	triggerd := false
	bCnt := 0.0
	wCnt := 0.0

	for _, r := range s {
		if r == '#' {
			if !triggerd {
				bCnt++
			}
			preBlacked = true
		} else {
			if preBlacked || triggerd {
				triggerd = true
				wCnt++
			}
			preBlacked = false
		}
	}

	fmt.Println(math.Min(bCnt, wCnt))
}