#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>
#include <iomanip>
#include <stack>
#include <queue>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <fstream>
#include <chrono>
#include <random>
#include <bitset>
//#include <atcoder/all>
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((int)(x).size())
#define pb push_back
using ll = long long;
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
ll gcd(ll a, ll b) {return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) {return a/gcd(a,b)*b;}

int main(){
  int N,M; cin >> N >> M;
  vector<pair<int,int>> E(M);
  rep(i,M){
    int a,b; cin >> a >> b; a--; b--;
    E[i] = {a,b};
  }
  int m1 = M/2;
  int m2 = M-m1;
  vector<int> C(N);
  rep(i,N) cin >> C[i];
  ll x = 0;
  rep(i,N) x += (1LL<<i)*C[i];
  map<ll,int> mp1;
  rep(i,1<<m1){
    ll v = 0;
    rep(j,m1){
      if(i&(1<<j)){
        v ^= (1LL<<E[j].first) + (1LL<<E[j].second);
      }
    }
    if(mp1.count(v)){
      chmin(mp1[v],__builtin_popcount(i));
    }
    else mp1[v] = __builtin_popcount(i);
  }
  int ans = 1<<30;
  rep(i,1<<m2){
    ll v = 0;
    rep(j,m2){
      if(i&(1<<j)){
        v ^= (1LL<<E[m1+j].first) + (1LL<<E[m1+j].second);
      }
    }
    if(mp1.count(v^x)){
      chmin(ans,mp1[v^x]+__builtin_popcount(i));
    }
  }
  if(ans==1<<30) cout << -1 << endl;
  else cout << ans << endl;
  return 0;
}