There are six plates next to each other in a row on a table. Bob grabs two plates and moves each plate one position to the left or to the right (if there is one plate or more at the target position then he puts the plate on the top). Repeating this procedure, can he stack the six plates into one single pile? (Bob can move one plate to the right and one plate to the left or both plates in the same direction but only the top plates).