A bookkeeping system indexes ledger entries starting from 1. An audit tool computes a checksum for any span of entries by XOR-ing together every index from l to r inclusive.
Given l and r, compute this checksum.
Input format
Line 1: two space-separated integers l r.
Output format
A single integer: the XOR of every integer from l to r inclusive.
Constraints
- 1 ≤ l ≤ r ≤ 2,000,000