The work that you do on the lever will be the same as the work done by the lever on the rock. This aligns with the Law of the Conservation of Energy which states that energy can not be created nor destroyed. Since work can be calculated as force applied over a distance, you will apply a smaller force but your distance will be longer. The lever will apply a greater force over a shorter distance in proportion to yours. Therefore, the same amount of work is done on both sides of the lever.