Codeforces Round #258 (Div. 2)Devu and Flowers Inclusion and Exclusion Principle_html/css_WEB-ITnose

Title: Codeforces Round #258 (Div. 2) Devu and Flowers Question meaning: n boxes, the i-th box has fi flowers, the flowers in each box are exactly the same, and the flowers in different boxes are different, find the following The number of options for removing s flowers from n boxes. n#include using namespace std;const int MOD = 1e9 + 7;typedef long long LL;LL invv[25];LL inv(LL x)/// 求逆元{ return x == 1 ? 1LL : (MOD - MOD / x) * inv (MOD % x) % MOD;}LL Cmn(LL n, LL m) ///求组合数{ LL ret = 1; for (int i = 1; i > n >> s; for (int i = 0; i > a[i]; int ALL = (1