Please choose the correct ending to complete the given sentence: Health: [header] How to do advanced computer yoga [title] Use head tilts to stretch out your neck. [step] When practicing computer yoga, it's best to start at the head and move down. To do this, move your head in all directions by pushing your neck forwards and backwards and turning it from side to side.

Ending1: Try to make your motions gentle and calculated, not erratic or jerky, and give yourself ample time to complete each one. Every time you move to a new side, stretch your neck out as far as you can and hold it in place for 3 long, deep breaths. Ending2: [substeps] This is similar to the back tilt: rotate your head from side to side for about 20 seconds, then repeat on the other side. Avoid being stretched too tightly, as this could cause permanent damage. Ending3: Leaning forward causes larger blood vessels in your face, resulting in optical strain on you eyes and (eventually) headaches and cornea damage. [substeps] Keep your chin above your eyes as you sit, and tilt your head back slightly to counter the forces on your face. Ending4: Repeat 5 times (or as many as you can do at a time). You can use a straight back posture, by turning your face to the ceiling or on a cushion.

Answer format: ending1/ending2/ending3/ending4