reserve a,b,c,h for Integer;
reserve k,m,n for Nat;
reserve i,j,z for Integer;
reserve p for Prime;

theorem
  for x,y,z being Complex holds
  x^2+y^2+z^2+x+y+z = 1 iff (2*x+1)^2+(2*y+1)^2+(2*z+1)^2 = 7;
