//あとでしっかり詰める #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define all(a) a.begin(),a.end() #define rep(i, n) for (ll i = 0; i < (n); i++) #define pb push_back #define debug(x) cerr << #x << ':' << x << '\n' #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") using namespace std; typedef long long ll; typedef unsigned long long ull; typedef long double ld; typedef pair P; typedef complex com; constexpr int inf = 1000000010; constexpr ll INF = 1000000000000000010; constexpr ld eps = 1e-12; constexpr ld pi = 3.141592653589793238; template inline bool chmax(T &a, const U &b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(T &a, const U &b) { if (a > b) { a = b; return true; } return false; } constexpr ll mod = 1000000007; vector fac, inv, facinv; void modcalc(int modsize) { fac.resize(modsize); inv.resize(modsize); facinv.resize(modsize); fac[0] = 1; fac[1] = 1; inv[1] = 1; facinv[0] = 1; facinv[1] = 1; for (ll i = 2; i < modsize; i++) { fac[i] = fac[i - 1] * i % mod; inv[i] = mod - inv[mod % i] * (mod / i) % mod; facinv[i] = facinv[i - 1] * inv[i] % mod; } } ll modinv(ll a) { a %= mod; if (a == 0) abort(); if (a < (ll)inv.size()) return inv[a]; ll b = mod, u = 1, v = 0; while (b) { ll t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); } u %= mod; if (u < 0) u += mod; return u; } ll modpow(ll a, ll b) { ll ans = 1; a %= mod; while (b) { if (b & 1) ans = ans * a % mod; a = a * a % mod; b >>= 1; } return ans; } ll modcomb(ll n, ll k) { if (n < 0 || k < 0 || n < k) return 0; return fac[n] * facinv[k] % mod * facinv[n - k] % mod; } ll modperm(ll n, ll k) { if (n < 0 || k < 0 || n < k) return 0; return fac[n] * facinv[n - k] % mod; } ll modhom(ll n, ll k) { if (n < 0 || k < 0 || n == 0 && k > 0) return 0; if (n == 0 && k == 0) return 1; return fac[n + k - 1] * facinv[k] % mod * facinv[n - 1] % mod; } int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); modcalc(200010); vector sum(200010); rep(i, 200005) sum[i + 1] = (sum[i] + fac[i]) % mod; int n, m; cin >> n >> m; vector a(m), b(m); rep(i, m) { cin >> a[i] >> b[i]; a[i]--; b[i]--; } ll ng = 0; for (int i = 1; i < (1 << m); i++) { int pcnt = 0; rep(j, m) if ((i >> j) & 1) pcnt++; map> graph; map deg; rep(j, m) { if ((i >> j) & 1) { deg[a[j]]++; deg[b[j]]++; graph[a[j]].pb(b[j]); graph[b[j]].pb(a[j]); } } vector use; for (auto x : deg) use.pb(x.first); map vis; queue

que; int cycle = 0; int r = 0; bool ok = true; rep(j, use.size()) { int v = use[j]; if (!vis[v]) { r++; que.push({ v,-1 }); while (!que.empty()) { P p = que.front(); que.pop(); int nowv = p.first; int prev = p.second; vis[nowv] = true; int cnt = 0; for (int nxtv : graph[nowv]) { if (nxtv == prev) continue; cnt++; if (vis[nxtv] && nxtv != v) ok = false; if (nxtv == v) cycle++; if (!vis[nxtv]) { que.push({ nxtv,nowv }); } } if (cnt > 1) ok = false; } } } if (i == 1) debug(cycle), debug(r); if (cycle > 1) ok = false; if (cycle == 1 && r > 1) ok = false; ll res = 0; if (ok) { if (cycle == 1 && r == 1) res = 1; else { res = modpow(2, r - 1) * (sum[n - use.size() + r] - sum[r - 1] + mod) % mod; } } if (pcnt & 1) ng += res; else ng -= res; } ng %= mod; if (ng < 0) ng += mod; ll ans = 0; for (int i = 3; i <= n; i++) { ll c = fac[n] * facinv[n - i] % mod; c *= modinv(2); c %= mod; c *= modinv(i); c %= mod; ans += c; } ans -= ng; ans %= mod; if (ans < 0) ans += mod; cout << ans << '\n'; }