Mixing Lists

[consalo]

HI!

I'm a newbie with GH and recently I've been trying to mix 3 lists with
no results :(

The 3 lists are:
-ABCDEFG...
-ABCDEFG...
-ABCDEFG...

And I would like to get:
-AAABBBCCCDDDEEEFFFGGG...

Any suggestions?

Thanks! :)