Running and skipping are the best exercise.
In order to achieve the best results, it is recommended to exercise together with abdominal exercises, such as lying on your back and rolling your abdomen (see video: give you six abdominal muscles in eight minutes) for 20 to 30 minutes. If you insist on doing your best every day, if you don't have much energy, exercise at least every other day. One month makes the stomach disappear, and three months makes the sexy abdominal muscles come out.