#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll n, m; cin >> n >> m;
    vector<ll> a(m), b(m);
    rep(i, m){
        cin >> a[i] >> b[i];
        a[i]--; b[i]--;
    }

    vector<ll> c(n); rep(i, n) cin >> c[i];

    ll m1 = m/2, m2 = m - m1;
    map<ll, ll> dp2;
    rep(bit, (1<<m2)){
        ll bit2 = 0;
        ll cnt = 0;
        rep(i, m2){
            if((bit>>i)&1){
                bit2 = bit2 ^ (1<<a[m1+i]);
                bit2 = bit2 ^ (1<<b[m1+i]);
                cnt++;
            }
        }

        if(dp2.find(bit2)!=dp2.end()){
            dp2[bit2] = min(dp2[bit2], cnt);
        }else{
            dp2[bit2] = cnt;
        }
    }

    ll T = 0;
    for(ll i=n-1; i>=0; i--) T = 2*T + c[i];

    ll ans = INF;
    rep(bit, (1<<m1)){
        ll bit1 = 0;
        ll cnt = 0;
        rep(i, m1){
            if((bit>>i)&1){
                bit1 = bit1 ^ (1<<a[i]);
                bit1 = bit1 ^ (1<<b[i]);
                cnt++;
            }
        }

        if(dp2.find(bit1 ^ T) != dp2.end()){
            ans = min(ans, cnt+dp2[bit1 ^ T]);
        }
    }

    if(ans == INF) cout << -1 << endl;
    else cout << ans << endl;
}