#include<iostream>
#include<algorithm>
#include<stack>
#include<vector>
#include<set>
#include<string>
#include<cstdint>
#include<map>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int ans = 1e9;
    int n,m;
    cin>>n>>m;
    vector<pair<int,int>> a,b;
    for(int i = 0;i<m;i++){
        int u,v;
        cin>>u>>v;
        u--;v--;
        pair<int,int> now = make_pair(u,v);
        if(i&1) b.push_back(now);
        else a.push_back(now);
    }
    map<ll,int> memo;
    ll mask = 0;
    for(int i = 0;i<n;i++){
        int c;
        cin>>c;
        if(c) mask |= 1ll << i;
    }

    int use = a.size();
    for(int i = 0;i<1<<use;i++){
        ll now = 0;
        for(int j = 0;j<use;j++){
            if(~i>>j&1) continue;
            now ^= 1ll << a[j].first;
            now ^= 1ll << a[j].second;
        }
        if(memo.find(now)==memo.end()) memo[now] = __builtin_popcountll(i);
        else  memo[now] = min(memo[now],__builtin_popcountll(i));
        if(now==mask) ans = min(ans,__builtin_popcountll(i));
    }
    use = b.size();
    for(int i = 0;i<1<<use;i++){
        ll now = 0;
        for(int j = 0;j<use;j++){
            if(~i>>j&1) continue;
            now ^= 1ll << b[j].first;
            now ^= 1ll << b[j].second;
        }
        ll want = now ^ mask;
        if(want==0) ans = min(ans,__builtin_popcountll(i));
        if(memo.find(want)!=memo.end()) ans = min(ans,__builtin_popcountll(i)+memo[want]);
    }
    if(ans==1e9) ans = -1;
    cout<<ans<<endl;
}