#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <queue>
#include <map>
#include <vector>
#include <set>
#include <cmath>
#include <iomanip>
#include <algorithm>
//#include <priority_queue>
#include <stack>

using namespace std;
typedef long long ll;
typedef double db;


struct Node
{
	vector<pair<ll, ll>> to;
	ll val;
};

int n, m;
vector<Node> v;

ll bfs(pair<ll, ll> start)
{
	priority_queue<pair<ll, ll>> q;
	q.push(start);
	ll mx = start.first;
	while (!q.empty())
	{
		pair<ll, ll> n = q.top();
		q.pop();
		for (auto c : v[n.second].to)
		{
			mx = max(mx, n.first + c.first);
			q.push(make_pair(n.first + c.first, c.second));
		}
	}
	return mx;
}

int main()
{
	cin >> n >> m;
	v.resize(n);
	for (int i = 0; i < n; i++)
	{
		cin >> v[i].val;
	}
	for (int i = 0; i < m; i++)
	{
		ll a, b;
		cin >> a >> b;
		a--; b--;
		v[a].to.push_back(make_pair(v[b].val, b));
	}
	ll mx = -1;
	for (ll i = 0; i < n; i++)
	{
		mx = max(mx, bfs(make_pair(v[i].val, i)));
	}
	cout << mx;
}