#include <bits/stdc++.h>
using namespace std;
const int MAXN = 10005;

int w[MAXN];
vector<vector<int> > adj(MAXN);
int ans[MAXN];

int dfs(int cur) {
    if (ans[cur] != 0)
        return ans[cur];
    int res = 0;
    for (int i = 0; i < adj[cur].size(); ++i) {
        res = max(res, dfs(adj[cur][i]));
    }
    return ans[cur] = res + w[cur];
}

int main() {
    int N, M; cin >> N >> M;
    for (int i = 0; i < N; ++i)
        cin >> w[i];
    for (int i = 0; i < M; ++i) {
        int x, y; cin >> x >> y;
        adj[--y].push_back(--x);
    }
    for (int i = 0; i < N; ++i)
        dfs(i);
    int res = 0;
    for (int i = 0; i < N; ++i)
        res = max(res, ans[i]);
    cout << res;
    return 0;
}