origins = {
const tree0 = shortest_tree({ graph, origins: [A] }).next().value;
const B = d3.scan(tree0.cost.map(d => (isFinite(d) ? -d : 0)));
const tree1 = shortest_tree({ graph, origins: [B] }).next().value;
const C = d3.scan(tree1.cost.map(d => (isFinite(d) ? -d : 0)));
const tree2 = shortest_tree({ graph, origins: [C] }).next().value;
const D = d3.scan(tree2.cost.map(d => (isFinite(d) ? -d : 0)));
return [C, D].sort();
}