Geocache, MD5, some parts of password known some parts not

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sounds like fun!

so x, y and z are just numbers?

for example if xx is always exactly 2 numbers you just replace the x with ?d
same for y and z, a, b and c.

example mask: N.?d?d.?d?d.?d?d?d

When you're done with that range, you do another run with E: E.?d?d.?d?d.?d?d?d