#pragma warning(disable:4786)
#pragma warning(disable:4996)
#include<list>
#include<bitset>
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<functional>
#include<string>
#include<cstring>
#include<cstdlib>
#include<queue>
#include<utility>
#include<fstream>
#include<sstream>
#include<cmath>
#include<stack>
#include<assert.h>
using namespace std;

#define MEM(a, b) memset(a, (b), sizeof(a))
#define CLR(a) memset(a, 0, sizeof(a))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define ABS(X) ( (X) > 0 ? (X) : ( -(X) ) )
#define S(X) ( (X) * (X) )
#define SZ(V) (int )V.size()
#define FORN(i, n) for(i = 0; i < n; i++)
#define FORAB(i, a, b) for(i = a; i <= b; i++)
#define ALL(V) V.begin(), V.end()
#define IN(A, B, C)  ((B) <= (A) && (A) <= (C))

typedef pair<int,int> PII;
typedef pair<double, double> PDD;
typedef vector<int> VI;
typedef vector<PII > VP;

#define AIN(A, B, C) assert(IN(A, B, C))

//typedef int LL;
typedef long long int LL;
//typedef __int64 LL;

const LL mod = 1000000007;
LL bigmod(LL a, LL b) {
	if (b == 0) return 1;
	LL x = bigmod(a, b / 2);
	x = (x * x) % mod;
	if (b & 1) x = (x * a) % mod;
	return x;
}

int n, m, k;
LL v[100005];
int s[100005];

VI V[100005];

int mark[100005], vis[100005];

void flood() {
	for (int i = 1; i <= n; i++) {
		if (!mark[i]) continue;
		for (int v : V[i]) {
			vis[v] = 1;
		}
	}
}

VI G[100005];
int cnt[100005];
LL p2[100005];

int main()
{
	scanf("%d %d %d", &n, &m, &k);
	for (int i = 1; i <= n; i++) scanf("%lld", &v[i]);
	for (int i = 1; i <= k; i++) scanf("%d", &s[i]);
	for (int i = 1; i <= m; i++) {
		int u, v;
		scanf("%d %d", &u, &v);
		V[u].push_back(v);
		V[v].push_back(u);
	}

	for (int i = 1; i <= k; i++) {
		mark[s[i]] = 1;
	}
	flood();
	for (int i = 1; i <= n; i++) {
		if (vis[i] && v[i] && !mark[i]) {
			printf("-1\n");
			return 0;
		}
	}

	for (int i = 1; i <= k; i++) {
		int u = s[i];
		for (int v : V[u]) {
			G[v].push_back(cnt[v]);
		}
		cnt[u]++;
	}

	p2[0] = 1;
	for (int i = 1; i <= MAX(n, k); i++) {
		p2[i] = (p2[i - 1] * 2) % mod;
	}
	LL ans = 0;
	for (int i = 1; i <= n; i++) {
		LL now = 0;
		for (int x : G[i]) {
			now = (now + p2[cnt[i] - x]);
		}
		now %= mod;
		now = (now * v[i]) % mod;
		now = (now * bigmod(p2[cnt[i]] + mod - 1, mod - 2)) % mod;
		ans += now;
	}
	ans %= mod;
	printf("%lld\n", ans);
	return 0;
}