Types: N: int, M: int, Xi: List[int], Yi: List[int]
Ranges: 2 ≤ N ≤ 10^6, 0 ≤ M ≤ 50, 1 ≤ Xi, Yi ≤ N
Addtl Info: i ≠ j implies (Xi, Yi) ≠ (Xj, Yj), (Xi, Yi) ≠ (1, 1), (Xi, Yi) ≠ (N, N)