mod = 998244353 R = 3 Rinv = 332748118 W = [pow(R, (mod-1)>>i, mod) for i in range(24)] Winv = [pow(Rinv, (mod-1)>>i, mod) for i in range(24)] def fft(k, f): for l in range(k, 0, -1): d = 1<