「codeforces - 407E」k-d-sequence
link.不错的题.改写条件.我们称一个区间 $[l, r)$ 是合法的当且仅当 $\forall i \in [l, r)$,有 $a_i \equiv k \pmod d$,$\not\ex...
In mathematics you don't understand things, you just get used to them.
In mathematics you don't understand things, you just get used to them.