A: f(x1, x2, x3, ..., xn)
B: f(y1, y2, y3, ..., yn)
for x1 = y1, x2 = y2, ..., xn-1 = yn-1, but xn != yn
if f(x1, x2, x3, ..., xn) > f(y1, y2, y3, ..., yn) then A
if f(x1, x2, x3, ..., xn) < f(y1, y2, y3, ..., yn) then B
if f(x1, x2, x3, ..., xn) = f(y1, y2, y3, ..., yn) then both |