This ab exercise flattens your belly and helps you get a slimmer waist.

Windshield Wiper
Step 1
Lie on your back with knees bent to 90-degree angles.
Step 2
Straighten your arms by your sides, and lengthen your fingertips.
Step 3
Press the backs of your shoulders against a mat, and slide them down away from your ears.
Step 4
Focusing on the deep waist muscles, inhale and slowly move your knees to the right, then exhale and return to starting position. Repeat on the left; that’s 1 rep. Do 3–5 reps.

Source: Health