#include #include typedef long long int ll; using namespace std; typedef pair P; using namespace atcoder; template using min_priority_queue = priority_queue, greater>; #define USE998244353 #ifdef USE998244353 const ll MOD = 998244353; using mint = modint998244353; #else const ll MOD = 1000000007; using mint = modint1000000007; #endif const int MAX = 2000005; long long fac[MAX], finv[MAX], inv[MAX]; void COMinit() { fac[0] = fac[1] = 1; finv[0] = finv[1] = 1; inv[1] = 1; for (int i = 2; i < MAX; i++){ fac[i] = fac[i - 1] * i % MOD; inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD; finv[i] = finv[i - 1] * inv[i] % MOD; } } long long COM(int n, int k){ if (n < k) return 0; if (n < 0 || k < 0) return 0; return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD; } ll gcd(ll x, ll y) { if (y == 0) return x; else if (y > x) { return gcd (y, x); } else return gcd(x % y, y); } ll lcm(ll x, ll y) { return x / gcd(x, y) * y; } ll my_sqrt(ll x) { // ll m = 0; ll M = 3000000001; while (M - m > 1) { ll now = (M + m) / 2; if (now * now <= x) { m = now; } else { M = now; } } return m; } ll keta(ll num, ll arity) { ll ret = 0; while (num) { num /= arity; ret++; } return ret; } ll ceil(ll n, ll m) { // n > 0, m > 0 ll ret = n / m; if (n % m) ret++; return ret; } ll pow_ll(ll x, ll n) { if (n == 0) return 1; if (n % 2) { return pow_ll(x, n - 1) * x; } else { ll tmp = pow_ll(x, n / 2); return tmp * tmp; } } vector compress(vector& v) { // [3 5 5 6 1 1 10 1] -> [1 2 2 3 0 0 4 0] vector u = v; sort(u.begin(), u.end()); u.erase(unique(u.begin(),u.end()),u.end()); map mp; for (int i = 0; i < u.size(); i++) { mp[u[i]] = i; } for (int i = 0; i < v.size(); i++) { v[i] = mp[v[i]]; } return v; } int main() { int n, m; cin >> n >> m; vector a(m); vector b(m); for (int i = 0; i < m; i++) { cin >> a[i] >> b[i]; a[i]--; b[i]--; } vector c(n); for (int i = 0; i < n; i++) { cin >> c[i]; } vector> former; vector> latter; int fonum = m / 2; int lanum = m - m / 2; for (int i = 0; i < (1 << fonum); i++) { vector reverse(n, 0); for (int j = 0; j < fonum; j++) { if ((i >> j) & 1) { reverse[a[j]] = 1 - reverse[a[j]]; reverse[b[j]] = 1 - reverse[b[j]]; } } former.push_back(reverse); } for (int i = 0; i < (1 << lanum); i++) { vector reverse(n, 0); for (int j = 0; j < lanum; j++) { if ((i >> j) & 1) { reverse[a[fonum + j]] = 1 - reverse[a[fonum + j]]; reverse[b[fonum + j]] = 1 - reverse[b[fonum + j]]; } } latter.push_back(reverse); } int ans = 100000; for (int i = 0; i < (1 << fonum); i++) { for (int j = 0; j < (1 << lanum); j++) { int cnt = 0; for (int k = 0; k < fonum; k++) { if ((i >> k) & 1) cnt++; } for (int k = 0; k < lanum; k++) { if ((j >> k) & 1) cnt++; } vector cur = c; for (int k = 0; k < n; k++) { if (former[i][k] != latter[j][k]) { cur[k] = 1 - cur[k]; } } bool ok = true; // cout << i << ' ' << j << endl; for (int k = 0; k < n; k++) { // cout << cur[k] << ' '; if (cur[k]) ok = false; } // cout << endl; if (ok) ans = min(ans, cnt); } } if (ans == 100000) { cout << -1 << endl; } else { cout << ans << endl; } return 0; }