st: String Problem

["Raphael Fraser" <raphael.fraser@gmail.com>]

I have the following string variable code and would like to create the
variable pain. Code is a combination of two digit codes (1 letter,1
number) lumped together as many 6 codes can be combined.

code             pain
Z1D4             1
Y1                 0
H4T2D4F7      1
D4D5             1

I am not sure what combination of string functions to use. Can anyone help?

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