15 sets to failure, 2 minutes between sets, first 5 sets pull-ups, the rest chin-ups:

3 - 2 - 2 - 1 - 1 - 3 - 2 - 2 - 2 - 2 - 2 - 2 - 2 - 2 - 1.

Clearly, as one would expect, some of the same muscles are involved.