__H2
__H1(a) = __H2(a) = __H3(a) = 0;
__H1(a) = __H2(a) = __H3(a) = 0;
__H2(a) = x2;
__H2(a) = x2;
x2 = __H2(x);
y2 = __H2(y);
__H1(a) = __H2(a) = __H3(a) = 0;
__H1(a) = __H2(a) = __H3(a) = 0;
__H2(a) = x2;
__H2(a) = x2;
x2 = __H2(x);
y2 = __H2(y);