#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N, M;
	cin >> N >> M;
	long long state_init = 0;
	vector<int> a(M), b(M);
	for( int i = 0; i < M; i++ ) {
		cin >> a[i] >> b[i];
		a[i]--, b[i]--;
	}
	for( int i = 0; i < N; i++ ) {
		long long c;
		cin >> c;
		state_init |= c<<i;
	}
	int m1 = M/2, m2 = (M+1)/2, ans = 100;
	map<long long, int> mp;
	for( int S = 0; S < 1<<m1; S++ ) {
		long long state = 0;
		for( int i = 0; i < m1; i++ ) {
			if( (S>>i)&1 ) {
				state ^= 1LL<<a[i];
				state ^= 1LL<<b[i];
			}
		}
		if( !mp.count(state) ) {
			mp[state] = M;
		}
		mp[state] = min(mp[state], __builtin_popcount(S));
	}
	for( int S = 0; S < 1<<m2; S++ ) {
		long long state = 0;
		for( int i = m1; i < m1+m2; i++ ) {
			if( (S>>(i-m1))&1 ) {
				state ^= 1LL<<a[i];
				state ^= 1LL<<b[i];
			}
		}
		if( mp.count(state^state_init) ) {
			ans = min(ans, mp[state^state_init]+__builtin_popcount(S));
		}
	}
	if( ans == 100 ) {
		cout << -1 << endl;
	}else {
		cout << ans << endl;
	}
}