Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to do side planks with an exercise ball [title] Put your exercise ball in an open area. [step] You should have plenty of free space to move around, and all sharp/heavy objects should be removed so as to minimize the potential for accidents. [title] Kneel on an exercise mat with the exercise ball next to you.

Ending1: [step] Keep your knees firmly planted on the mat and your knees lined up with the balls of your feet. [title] Position your hips so they're above hip level. Ending2: [step] Keep your hands palm down and knees bent up. Put your entire right foot on the mat and perform a side plank step by step with your left foot. Ending3: [step] It doesn't matter which side the ball is on first since you'll eventually work out both sides for this exercise. [title] Lower your upper body to drape over the exercise ball. Ending4: [step] It's good for both feet. [title] Balance your exercise ball mid-plank.

Answer format: ending1/ending2/ending3/ending4