Subsetting an array with unknown array size

I want to select elements in an array that meet a certain condition.

program subsetting

implicit none
real,dimension(100)::A
! I declare an array(say,B) elements of which are greater than 0.15 in A

call random_number(A)
! I have to select elements that are greater than 0.15 and store them in B

end program subsetting

The problem here is that I don't know how many elements are greater than 0.15. How can I write a code for getting the array B?