// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
using namespace std;

using P = pair<int, int>;

const int M = 998244353;
const long long LM = 1LL << 60;


int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    int n, m;
    cin >> n >> m;
    vector<P> edges(m);
    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        edges[i] = { u, v };
    }
    vector<int> c(n);
    long long st = 0;
    for (int i = 0; i < n; ++i) {
        cin >> c[i];
        if (c[i] == 1) {
            st ^= 1LL << i;
        }
    }
    int n1 = m / 2;
    int n2 = m - n1;
    unordered_map<long long, int> mp;
    for (int i = 0; i < (1 << n1); ++i) {
        long long p = 0;
        int c = 0;
        for (int j = 0; j < n1; ++j) {
            if ((i >> j) & 1) {
                p ^= (1LL << edges[j].first) ^ (1LL << edges[j].second);
                ++c;
            }
        }
        if (!mp.count(p)) {
            mp[p] = c;
        }
        mp[p] = min(mp[p], c);
    }
    int ans = M;
    for (int i = 0; i < (1 << n2); ++i) {
        long long p = 0;
        int c = 0;
        for (int j = 0; j < n2; ++j) {
            if ((i >> j) & 1) {
                p ^= (1LL << edges[n1 + j].first) ^ (1LL << edges[n1 + j].second);
                ++c;
            }
        }
        if (mp.count(p ^ st)) {
            ans = min(ans, mp[p ^ st] + c);
        }
    }
    cout << (ans == M ? -1 : ans) << '\n';

    return 0;
}