A 1000 rep core workout all bodyweight. Start with 200 leg raises,followedd by 200 cross crunches, 200 crunches,200 heel touches, then 200 scissor kicks. You can take a 15-30 sec break every 100-200 reps depending on you but try to go through it without a break. When your ready give it another go around.The time depends on you good luck !