mpiexec can not execute ./a.out?

[acceleratedman]

i use the following command to compile the fortran program. no warning or errors

$ mpif77 -o greeting greeting.f


to execute
$ mpiexec -n 4 ./greeting

but it produce no results.. any1 can fix it? i think the program is ok. pls refer to the code in the attachment.
thanks in advance
pls reply in chinese...