_2sum
_2sum(sh, sl);
_2sum(ax2l, ay2l);
_2sum(sh, ax2l);
_2sum(sl, ay2l);
_2sum(sh, sl);
_2sum(ax2l, ay2l);
_2sum(sh, ax2l);
_2sum(sl, ay2l);
_2sum(sh, sl);
_2sum(ax2l, ay2l);
_2sum(sh, ax2l);
_2sum(sl, ay2l);