Yeah, you read well. It takes only 4 minutes in your day to have a flat the stomach of which you dreamed about all your life.
You have to admit that 4 minutes are something that all of us can spare from our everyday life. No excuses.
In doing so, this set of exercises is very simple because, in fact, it consists of a single exercise that is shown in the photo above, and the picture below is the plan with the timing in which you combine exercise and rest.
In case you need an extra incentive, take a look at the video in which you will be clarified of any ambiguity.