#pragma GCC optimize(2)

#pragma GCC optimize(3)

#pragma GCC optimize(4)

#include<bits/stdc++.h>

using namespace std;

#define fi first

#define se second

#define pi acos(-1.0)

#define LL long long

//#define mp make_pair

#define pb push_back

#define ls rt<<1, l, m

#define rs rt<<1|1, m+1, r

#define ULL unsigned LL

#define pll pair<LL, LL>

#define pii pair<int, int>

#define piii pair<pii, int>

#define mem(a, b) memset(a, b, sizeof(a))

#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);

//head

const int N = 3e5 + ;

int d[N];

vector<pii> g[N];

vector<int> ans;

bool vis[N];

void dfs(int u) {

    vis[u] = true;

    for (int i = ; i < g[u].size(); i++) {

        int v = g[u][i].fi;

        if(!vis[v]) {

            dfs(v);

            if(d[v] == ) {

                ans.pb(g[u][i].se);

                if(d[u] != -) d[u] ^= ;

            }

        }

    }

}

int main() {

    int n, m, u, v, sum = , rt = ;

    scanf("%d %d", &n, &m);

    for (int i = ; i <= n; i++) scanf("%d", &d[i]);

    for (int i = ; i <= n; i++) {

        if(d[i] != -) sum += d[i];

        else {

            rt = i;

            sum = ;

            break;

        }

    }

    for (int i = ; i <= m; i++) {

        scanf("%d %d", &u, &v);

        g[u].pb({v, i});

        g[v].pb({u, i});

    }

    if(sum&) puts("-1");

    else {

        dfs(rt);

        printf("%d\n", (int)ans.size());

        for (int i = ; i < ans.size(); i++) printf("%d\n", ans[i]);

    }

    return ;

}