fortran code, wrong output!!

[acceleratedman]

c********************************************************************
c complete fortran code
program hello
IMPLICIT NONE

include 'mpif.h'

integer ierr
integer my_rank
integer p

call MPI_INIT(ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD, my_rank, ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD, p, ierr)

write(6,900) p
900 format(' ','there are ', I1, ' processes')

if( my_rank .EQ. 0 ) then
write(6,*) 'hello world from process',my_rank
else
print *, 'hello world from other process'
endif

call MPI_FINALIZE(ierr)

stop
end program hello
c************************************************************

$ mpif77 -o hello hello.f
$ mpiexec -n 4 ./hello
there are 1 processes
hello world from process 0
there are 1 processes
hello world from process 0
there are 1 processes
hello world from process 0
there are 1 processes
hello world from process 0

what is wrong here? the program is supposed to simulate four CPUs. but there is only 1 process.
and the same message is printed four times. any1 can help??

[greco]

哇 fortran，不会