function small_to_big(xyz) {
const [x,y,z] = xyz;
const xh = my.div(y+shift*x, area),
yh = my.div(z+shift*y, area),
zh = my.div(x+shift*z, area);
const i = my.div(1+xh-yh, 3),
j = my.div(1+yh-zh, 3),
k = my.div(1+zh-xh, 3);
return [i,j,k,xh,yh,zh];
}