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: Wrong Answer)

def chec(s):
    llis = []
    rlis = []
    clis = 0
    lef = 0
    rig = 0
    rtmp = 0
    ltmp = 0
    flg = 0
    na = len(s)
    for i in reversed(range(0,na-1)):
        if i != na and s[i] == '#' and s[i+1] == '.' :
            #clis+= 1
            #print(i)
            rtmp = i+1
            ltmp = i
            while ltmp != -1 and s[ltmp] == '#':
                lef += 1
                ltmp -= 1
            llis.append(lef)
            while rtmp+1 != na and s[rtmp] == '.':
                rig += 1
                rtmp += 1
            rlis.append(rig)
            lef = 1
            rig = 1
            rtmp = 0
            ltmp = 0

    print(llis)
    print(rlis)
    clis = min(sum(llis),sum(rlis))
    return clis


n = int(input())
s = list(input())
print(chec(s))