program leap_year
       integer i
       write(*,*) "leap years are"
       do i = 1900,2005
       call leap(i)
       enddo
       end

       subroutine leap(i)
       integer i
       if (MOD(i,4).eq.0) then
         if (MOD(i,100).ne.0) then
            goto 20
         else
            if (MOD(i,400).eq.0) then
               goto 20
            endif
         endif
       else
         goto 30 
       endif
20     write(*,*) i 
30     return
       end