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 PyPy3 (7.3.0) (judge verdict: Wrong Answer)


import bisect

N = int(input())
S = '0'+input()+'0'

lst1 = []
lst2 = [0]*(N+2)


for i in range(1,N+1):
  if S[i] == '#':
    lst1.append(i)
  if S[N+1-i] == '.':
    lst2[N+1-i] = lst2[N+2-i] + 1
  else:
    lst2[N+1-i] = lst2[N+2-i]

if len(lst1) == N or lst2[1] == N:
  print(0)
  exit()
  
rlt = N+1
for i in range(len(lst1)):
  rlt =  min(rlt, i+lst2[lst1[i]])
  
print(rlt)