In the groups ( Z / n Z , + ) introduced above, the element 1 is primitive, so these groups are cyclic. Indeed, each element is expressible as a sum all of whose terms are ⁠ 1 ⁠. Any cyclic group with n elements is isomorphic to this group. A second example for cyclic groups is the group of ⁠ n ⁠ th complex roots of unity, given by complex numbers z satisfying ⁠ z n = 1 ⁠. These numbers can be visualized as the vertices on a regular n -gon, as shown in blue in the image for ⁠ n = 6 ⁠. The group operation is multiplication of complex numbers. In the picture, multiplying with z corresponds to a counter-clockwise rotation by 60°. From field theory, the group F p × × is cyclic for prime p : for example, if ⁠ p = 5 ⁠, 3 is a generator since ⁠ 3 1 = 3 ⁠, ⁠ 3 2 = 9 ≡ ≡ 4 ⁠, ⁠ 3 3 ≡ ≡ 2 ⁠, and ⁠ 3 4 ≡ ≡ 1 ⁠.