If z=cos(2π/7)+isin(2π/7)z = \cos(2\pi/7) + i\sin(2\pi/7)z=cos(2π/7)+isin(2π/7), find 1+z+z2+z3+z4+z5+z61+z+z^2+z^3+z^4+z^5+z^61+z+z2+z3+z4+z5+z6.
111
000
zzz
777