ZigZag Tree Sequences (Easy)

**This is the easy version of the problem. In this version, the labels of the nodes $A_i$ satisfy $A_i \le 2$. This problem is worth $100$ points in divisions $2, 3$ and $4$, and $35$ points in division $1$.** You are given a labeled tree on $N$ nodes. Node $i$ has the label $A_i$. Count the number of zig-zag sequences in it. Formally, a sequence of nodes $v_1, v_2, v_3, \ldots, v_k$ of len