from typing import List, Tuple N_MAX = 13 popcount = [0] * (1 << N_MAX) for S in range(1, 1 << N_MAX): popcount[S] = popcount[S & (S - 1)] + 1 def subset_zeta(f: List[int]): """ Inplace conversion from f to ζf. ζf is defined as follows: (ζf)(S) = Σ[T⊆S] f(T) """ n = len(f) block = 1 while block < n: offset = 0 while offset < n: for p in range(offset, offset + block): f[p + block] += f[p] offset += 2 * block block <<= 1 def ranked_zeta(f: List[List[int]]): """ Inplace conversion from f to ζf. ζf is defined as follows: (ζf)(S) = Σ[T⊆S] f(T) """ n = len(f) block = 1 while block < n: offset = 0 while offset < n: for p in range(offset, offset + block): a = f[p + block] b = f[p] for i in range(N_MAX + 1): a[i] += b[i] offset += 2 * block block <<= 1 def ranked_mobius(f: List[List[int]]): """ Inplace conversion from f to μf. μf is defined as follows: (μf)(S) = Σ[T⊆S] (-1)^(|S/T|) f(T) """ n = len(f) block = 1 while block < n: offset = 0 while offset < n: for p in range(offset, offset + block): a = f[p + block] b = f[p] for i in range(N_MAX + 1): a[i] -= b[i] offset += 2 * block block <<= 1 def add_rank(f: List[int]): """ Add rank """ return [[(i == popcount[S]) * f[S] for i in range(N_MAX + 1)] for S in range(len(f))] def remove_rank(rf: List[List[int]]): """ Remove rank """ return [rf[S][popcount[S]] for S in range(len(rf))] def subset_exp(f: List[int]): """ Subset subset_exp of Σ[S⊆{0,1,...,n-1}] f(S) """ assert f[0] == 0 n = 0 while 1 << n != len(f): n += 1 rf = add_rank([1]) for i in range(n): rg = add_rank(f[1 << i: 1 << (i + 1)]) ranked_zeta(rg) for S in range(1 << i): rf[S].append(0) rg[S].insert(0, 1) a = rf[S] b = rg[S] for k in reversed(range(i + 2)): v = 0 for x in range(k + 1): v += a[k - x] * b[x] b[k] = v rf.append(b) ranked_mobius(rf) return remove_rank(rf) def count_cycles(n: int, edges: List[Tuple[int, int]]): cycle = [0] * (1 << n) adj = [[] for _ in range(n)] for u, v in edges: adj[u].append(v) adj[v].append(u) cycle_dp = [[0] * n for _ in range(1 << n)] for v in range(n): cycle_dp[1 << v][v] = 1 for s in range(1, 1 << n): start = 0 while not ((s >> start) & 1): start += 1 for cur in range(n): if cycle_dp[s][cur] == 0: continue for nxt in adj[cur]: if start == nxt: cycle[s] += cycle_dp[s][cur] elif start < nxt and not ((s >> nxt) & 1): cycle_dp[s | (1 << nxt)][nxt] += cycle_dp[s][cur] for s in range(1, 1 << n): if popcount[s] == 1: cycle[s] = 1 elif popcount[s] == 2: cycle[s] = 0 else: cycle[s] //= 2 return cycle if __name__ == '__main__': n, m = map(int, input().split()) edges = [] for _ in range(m): u, v = map(int, input().split()) u -= 1 v -= 1 edges.append((u, v)) # E[S] = # of edges connecting vertices in S E = [0] * (1 << n) for u, v in edges: E[(1 << u) | (1 << v)] += 1 subset_zeta(E) cycle = count_cycles(n, edges) f = [0] * (1 << n) for C in range(1, 1 << n): if cycle[C] == 0: continue # max C t = C.bit_length() - 1 # {0, ..., tX} - C S = ((1 << (t + 1)) - 1) ^ C k = popcount[S] bit_deposit = [0] * (1 << k) bit_deposit[0] = S for A in range(1, 1 << k): bit_deposit[A] = (bit_deposit[A - 1] - 1) & S bit_deposit.reverse() g = [0] * (1 << k) for A in range(1 << k): g[A] = f[bit_deposit[A]] * (E[bit_deposit[A] | C] - E[bit_deposit[A]] - E[C]) for A, hA in enumerate(subset_exp(g)): f[bit_deposit[A] | C] += cycle[C] * hA print(subset_exp(f)[-1])