NEC-LIST: NEC2 input file error

Hi All,

I'm trying to use NEC2 for the first time. I want to see the 3d magnetic
  field of a single square loop. My input file (loop.in) is as follows:

CM My first go at an NEC input file. Single Square Loop.
CE
GW 1 4 -1 1 0 1 1 0 0.01
GW 2 5 1 1 0 1 -1 0 0.01
GW 3 4 1 -1 0 -1 -1 0 0.01
GW 4 4 -1 -1 0 -1 1 0 0.01
GE 0
FR 0 1 0 0 1
EX 0 2 3 0 1
NH 1 5 5 5 0 0 0 0.25 72 72
EN

When I pass this file to the NEC core, I get the following error:

fmt: end of file
apparent state: unit 1 named loop.in
last format: (a)
lately reading sequential formatted external IO
Aborted

Anyone know what is wrong?

Also, are there any GPL / freeware programs for automating the
production of these input files?

Thanks.
James.

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