A diamond of numbers is an arrangement of circles in the shape of a trapezoid (see figure) in which the number in any circle above its central (longest) row is the sum of the two numbers in the circles that it lies on, while the number in any circle below the central row is the (absolute) difference of the two numbers in the circles that lie on it. The diamond is perfect if all the numbers used are different positive integers.
What is the least number that can occupy the top circle of a perfect diamond whose central row consists of four circles?
What if the central row consists of 5 or 6 circles?
