@[PorkSausage](/user/974277) `add(1, 1, n, x, x, y - a[x]);`中`y-a[x]`可能是负数，然后将cal函数里的x加上mod即可。
by __zaa__ @ 2024-04-24 22:00:33
@[__zaa__](/user/716965) %%%%太神了
by PorkSausage @ 2024-04-24 22:10:48