Compute an array <code>even</code> where <code>even[u]</code> is the number of nodes at an even distance from node <code>u</code>, for every <code>u</code> of the first tree.

Compute an array <code>odd</code> where <code>odd[u]</code> is the number of nodes at an odd distance from node <code>u</code>, for every <code>u</code> of the second tree.