#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int MOD = 998244353;
const ll baza = (1LL << 32);

int add (int a, int b) {
    return (ll) ((ll) a + b + MOD) % MOD;
}

int mull (int a, int b) {
    return (ll) ((ll) a * b) % MOD;
}

struct big_num {
    vector<ll> zn;

    void ocisti () {
        ll vis = 0;
        for (ll &x: zn) {
            x += vis;
            vis = x >> baza;
            x &= (1LL << baza) - 1;
        }
        if (vis) zn.push_back (vis);
    }

    void mul (ll y) {
        for (ll &x: zn) x *= y;
        ocisti ();
    }

    void operator += (const big_num & rhs) {
        while (zn.size () < rhs.zn.size ()) zn.push_back (0);

        for (int i = 0; i < rhs.zn.size (); i++) {
            zn[i] += rhs.zn[i];
        }
        ocisti();
    }

    void jedan () {
        ocisti ();
        zn.push_back (1);
    }

    int log () {
//        cout << zn.back () << ' ' << log2(zn.back()) << "\n";
        int sum = 0;
        for (int i = 0; i < zn.size () - 1; i++) {
            sum = add (sum, 32);
        }
        sum = add (sum, ceil(log2(zn.back () + 1)));
        return sum;
    }
};

const int MAXN = 1e4 + 500;
const int MAXM = 1e5 + 500;

int n, m, val[MAXN];
vector<int> children[MAXN], parents[MAXN];
int sink;
big_num dp[MAXN];
int bio[MAXN];
big_num uk;
vector<int> v;

void topsort (int x) {
    bio[x] = 1;
    for (auto it: children[x]) {
        if (bio[it] == 0) {
            topsort (it);
        }
    }
    v.push_back(x);
}

int main () {
    ios_base::sync_with_stdio (false);
    cin.tie (0);

    cin >> n >> m;

    for (int i = 0; i < n; i++) cin >> val[i];

    for (int i = 0; i < m; i++) {
        int a,b;
        cin >> a >> b;
        a--;b--;

        children[a].push_back (b);
        parents[b].push_back (a);
    }

    for (int i = 0; i < n; i++) {
        if (children[i].size () == 0) sink = i;
    }

    for (int i = 0; i < n; i++) {
        if (bio[i] == 0) topsort (i);
    }

    dp[sink].jedan ();
    for (auto x: v) {
        if (x != sink) dp[x].mul(2);
        for (auto it: parents[x]) dp[it] += dp[x];
    }

//    for (int i = 0; i < n; i++) cout << dp[i].visak() << ' ';
//    cout << "\n";

    for (int i = 0; i < n; i++) dp[i].mul (val[i]);
    for (int i = 0; i < n; i++) uk += dp[i];

    cout << uk.log();

    return 0;
}