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 Fortran (gfortran v4.8.4) (judge verdict: Wrong Answer)

program main
 implicit none

 integer N,M,i,j,k
 character*200000 Str
 read(*,*) N, Str
 j = 0
 do i=1,N
  if(Str(i:i) == '#') then
   M = i+1
   j=1
   exit
  end if
 end do

 if(j == 1) then
  k = 0
  do i=M,N
   if(Str(i:i) == '.') then
    k = k+1
   else
    j = j+1
   end if
  end do
  if(k == 0) then
   write(*,*) 0
  else
   write(*,*) min(j,k)
  end if
 else
  write(*,*) 0
 end if

end program main