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 Python (3.4.3) (judge verdict: Runtime Error)

a = input()
b = input()
c = list(b)
e = []
for i in range(len(c)+1):  #左からi個を白にする
    if i == 0: #全て黒に変える場合
        e.append(c.count("."))
        ans = e[0]
    else:
        if c[i-1] == ".":
            d = d + 1
        e.append(((i - d) + (c.count(".") - d)))
        if ans >= e[i]:
            ans = e[i]
print(ans)