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)

implicit none
integer n,k,i,slen
integer :: cnt=0,black=0,white=0
character(200000) s
logical :: cnc=.false.


read(5,*) n
read(5,*) s

slen=len_trim(s)

do i=1,slen

if(s(i:i).eq."#") then
black=black+1
else if(s(i:i).eq.".") then
white=white+1 
endif

if(s(i:i+1) .eq. "#.") then
cnc=.true.
else if (s(i:i+1) .eq. ".#" .and.  cnc) then
cnt=cnt+min(black,white)
white=0
black=0
cnc=.false.
endif

enddo

if(s(slen-1:slen).eq."#.") then
cnt=cnt+1
endif

write(6,*) cnt

end