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)

N = input()
S = input()
 
count = 0
for i in range(int(N)-1):
    if(S[i] == "#" and S[i+1] == "."): 
        S[i] = "."
        count += 1
for j in range(int(N)-1):
    if(S[j] == "#" and S[j+1] == "."): 
        S[j] = "."
        count += 1
for m in range(int(N)-1):
    if(S[m] == "#" and S[m+1] == "."): 
        S[m] = "."
        count += 1
for n in range(int(N)-1):
    if(S[n] == "#" and S[n+1] == "."): 
        S[n] = "."
        count += 1
for k in range(int(N)-1):
    if(S[k] == "#" and S[k+1] == "."): 
        count += 1
 
print(count)