Types: y1: int, m1: int, d1: int, y2: int, m2: int, d2: int
Ranges: y1, y2 ≥ 0, 1 ≤ m1, m2 ≤ 12, 1 ≤ d1, d2 ≤ 31
Addtl Info: The number of datasets will not exceed 50; an input terminates when any value is negative; y1, m1, d1 ≤ y2, m2, d2