Race to complete 100 pullups... do a max set of pull-ups. Then drop down and do 30 pushups and 30 sit-ups. You will do a set of pushups and sit-ups for every set of pull-ups. The more sets it takes you to complete your pull-ups, the more other work you will do. Even if you are down to sets of 1-2 pull-ups, you will have to pay for each set.