This exercise is great for your abdominal muscles, especially for your side abdominal muscles.
Lie on your back and put your hands behind your head with fingers overlapping. Raise your upper body 2 to 3 inches. Raise your right leg, so your right calf is parallel with the floor and forming 90 degree angle in you knee. Raise your left leg approximately 5 inches of the floor and straighten it with toes pointing forward.
Curl up and raise your body for additional 3 inches.