constexpr int N = 3e6 + 10; ll fact[N], factrev[N + 1], s[N + 1]; void prep() { fact[0] = factrev[0] = 1; for (int i = 1; i < N; ++i) { fact[i] = (fact[i - 1] * i) % MDL; } s[0] = 1; for (int i = 1; i <= N; ++i) { s[i] = s[i - 1] * fact[i - 1] % MDL; } factrev[N] = inverse(s[N], MDL); for (int i = N; i; --i) { factrev[i - 1] = factrev[i] * fact[i - 1] % MDL; } for (int i = 0; i < N; ++i) { factrev[i] = factrev[i + 1] * s[i] % MDL; } }