Four minus three, absolute value, that's another one. So you see in this case, every data point was exactly one away from the mean. And we took the absolute value so that we don't have negative ones here. We just care how far it is in absolute terms. So you have four data points. Each of their absolute deviations is four away, so the mean of the absolute deviations are one plus one plus one plus one, which is four, over four. So it's equal to one.