Bus Routes

Diana is planning to make a very long journey. Her journey consists of $N$ bus routes, numbered from $1 to N$ in the order she must take them. The buses themselves are very fast but do not run often. The $i-th$ bus route only runs every $Xi$ days. More specifically, she can only take the $i-th$ bus on day $Xi, 2Xi, 3Xi$, and so on. Since the buses are very fast, she can take multiple buses on t