#include<bits/stdc++.h>

using namespace std;

struct edge
{
	int u, v;
};

int n, m, cnt, cnt2;
int low[100005], dfn[100005], s[100005], a[100005];
int in[100005], dis[100005];
vector<edge> G[100005], G2[100005];
bool instack[100005];
stack<int> stk;

void tarjan(int u)
{
	cnt ++;
	dfn[u] = low[u] = cnt;
	instack[u] = true;
	stk.push(u);
	for (int i = 0 ; i < G[u].size() ; i ++)
	{
		int v = G[u][i].v;
		if (!dfn[v])
		{
			tarjan(v);
			low[u] = min(low[u], low[v]);
		}
		else if (instack[v])
		{
			low[u] = min(low[u], dfn[v]);
		}
	}
	if (low[u] == dfn[u])
	{
		int node;
		while (node = stk.top())
		{
			instack[node] = false;
			s[node] = u;
			if (node == u)
			{
				break;
			}
			a[u] += a[node];
			stk.pop();
		}
	}
}

int topo()
{
	queue<int> que;
	for (int i = 1 ; i <= n ; i ++)
	{
		if (in[i] == 0 && s[i] == i)
		{
			que.push(i);
			dis[i] = a[i];
		}
	}
	while (!que.empty())
	{
		int k = que.front();
		que.pop();
		for (int i = 1 ; i <= G2[k].size() ; i ++)
		{
			int v = G2[k][i].v;
			dis[v] = max(dis[v], dis[k] + a[v]);
            in[v] --;
            if(in[v] == 0)
			{
				que.push(v);
			}
		}
	}
	int ans = 0;
    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 ++)
	{
		int x, y;
		cin >> x >> y;
		G[x].push_back({x, y});
	}
	for (int i = 1 ; i <= n ; i ++)
	{
		if (!dfn[i])
		{
			tarjan(i);
		}
	}
	for (int i = 1 ; i <= m ; i ++)
	{
		for (int j = 0 ; j < G[i].size() ; j ++)
		{
			int x = G[i][j].u, y = G[i][j].v;
			int x2 = s[x], y2 = s[y];
			if (x2 != y2)
			{
				G2[x2].push_back({x2, y2});
				in[y2] ++;
			}
		}
	}
	cout << topo();
	return 0;
}