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(8) N, nd, ns, i, firsts, nd2,ans, finald, ns2
  !integer loc(4) loc2(4) !left ., left #, right ., right #
  character(2*(10**5)) S
  read(*, *) N
  read(*, *) S
  nd = 0
  ns = 0
  firsts = N
  finald = 1
  ns2 = 0
  nd2 = 0
  do i = 1,N
    if (S(i:i) == '.') then
      nd = nd + 1
    else
      ns = ns + 1
    end if
  end do
  !if (ns /= 0) then
    do i = 1,N
      if (S(i:i) == '#') then
        firsts = i
        exit
      end if
    end do

      do i = firsts,N
        if (S(i:i) == '.') then
          nd2 = nd2 + 1
        end if
      end do

  !end if
  !if (nd /= 0) then
    do i = 1,N
      if (S(i:i) == '.') then
        finald = i
      end if
    end do
      do i = 1,finald
        if (S(i:i) == '#') then
          ns2 = ns2 + 1
        end if
      end do

  
  ans = min(nd, ns, nd2, ns2)
  write(*,'(i0)') ans
end program main