rt，样例输出 0。

#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
struct edge {
	int pos, to, next;
} e[N << 1], e2[N << 1];
int n, m, u, v, ans, tot, cnt, cnt2, cnts, dis[N], a[N], deg[N], dfn[N], low[N], pos[N], head[N], head2[N];
bool vis[N];
stack<int> s;
queue<int> q;
void add(int u, int v) {
	e[++ cnts].to = v;
	e[cnts].pos = u;
	e[cnts].next = head[u];
	head[u] = cnts;
}
void add2(int u, int v) {
	e2[++ cnt2].to = v;
	e2[cnt2].pos = u;
	e2[cnt2].next = head2[u];
	head2[u] = cnt2;
}
void tarjan(int u) {
	dfn[u] = low[u] = ++ tot;
	s.push(u), vis[u] = true;
	for (int i = head[u]; i; i = e[i].next) {
		int v = e[i].to;
		if (!dfn[v]) tarjan(v), low[u] = min(low[u], low[v]);
		else if (vis[v]) low[u] = min(low[u], low[v]);
	}
	if (dfn[u] == low[u]) {
		while (s.top() != u) {
			int v = s.top(); s.pop();
			pos[v] = u, vis[v] = false, a[u] += a[v];
		}
		s.pop(), pos[u] = cnt, vis[u] = false;
	}
}
int topo_sort() {
	for (int i = 1; i <= n; i ++)
		if (pos[i] == i && !deg[i]) q.push(i), dis[i] = a[i];
	while (!q.empty()) {
		int u = q.front(); q.pop();
		for (int i = head2[u]; i; i = e2[i].next) {
			int v = e2[i].to;
			dis[v] = max(dis[v], dis[u] + a[v]), deg[v] --;
			if (!deg[v]) q.push(v);
		}
	}
	for (int i = 1; i <= n; i ++)
		ans = max(ans, dis[i]);
	return ans;
}
int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i ++)
		cin >> a[i];
	for (int i = 1; i <= m; i ++)
		cin >> u >> v, add(u, v);
	for (int i = 1; i <= n; i ++)
		if (!dfn[i]) tarjan(i);
	for (int i = 1; i <= m; i ++) {
		int u = pos[e[i].pos], v = pos[e[i].to];
		if (u != v) add2(u, v), deg[v] ++;
	}
	cout << topo_sort() << '\n';
	return 0;
}