module gcd_module
implicit none

contains
  pure integer function gcd(a,b)
  implicit none
  integer, intent (in) :: a, b
  integer :: temp

    if (a<b) then
      temp = a
    else
      temp = b
    end if
    do while ((mod(a,temp)/=0) .or. (mod(b,temp)/=0))
      temp = temp - 1
    end do
    gcd = temp
  end function gcd
end module gcd_module

program ch1212
use gcd_module
implicit none
integer :: i, j, result

  print *, ' type in two integers'
  read *, i, j
  result = gcd(i,j)
  print *, ' gcd is ', result
end program ch1212