using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;
namespace Tasks
{
public class E
{
public static void Main(string[] args)
{
var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
Console.SetOut(sw);
Solve();
Console.Out.Flush();
}
public static void Solve()
{
var (N, M) = Scanner.Scan<int, int>();
var H = Scanner.ScanEnumerable<long>().ToArray();
var G = new List<(int, long)>[N].Select(x => new List<(int, long)>()).ToArray();
for (var i = 0; i < M; i++)
{
var (u, v) = Scanner.Scan<int, int>();
u--; v--;
G[u].Add((v, Math.Max(0, H[v] - H[u])));
G[v].Add((u, Math.Max(0, H[u] - H[v])));
}
var costs = new long[N];
Array.Fill(costs, long.MaxValue);
costs[0] = 0;
var queue = new PriorityQueue<(int U, long Cost)>((x, y) => x.Cost.CompareTo(y.Cost));
queue.Enqueue((0, 0));
while (queue.Count > 0)
{
var (u, cu) = queue.Dequeue();
if (costs[u] < cu) continue;
foreach (var (v, cv) in G[u])
{
var c = costs[u] + cv;
if (costs[v] <= c) continue;
costs[v] = c;
queue.Enqueue((v, c));
}
}
var answer = 0L;
for (var i = 0; i < N; i++)
{
answer = Math.Max(answer, H[0] - H[i] - costs[i]);
}
Console.WriteLine(answer);
}
public class PriorityQueue<T> : IReadOnlyCollection<T>
{
private readonly Comparison<T> _comparison;
private readonly List<T> _heap;
public PriorityQueue(IEnumerable<T> items, IComparer<T> comparer = null) : this(comparer)
{
foreach (var item in items) Enqueue(item);
}
public PriorityQueue(IEnumerable<T> items, Comparison<T> comparison) : this(comparison)
{
foreach (var item in items) Enqueue(item);
}
public PriorityQueue(IComparer<T> comparer = null) : this((comparer ?? Comparer<T>.Default).Compare) { }
public PriorityQueue(Comparison<T> comparison)
{
_heap = new List<T>();
_comparison = comparison;
}
public int Count => _heap.Count;
public IEnumerator<T> GetEnumerator() => _heap.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
public void Enqueue(T item)
{
var child = Count;
_heap.Add(item);
while (child > 0)
{
var parent = (child - 1) / 2;
if (_comparison(_heap[parent], _heap[child]) <= 0) break;
(_heap[parent], _heap[child]) = (_heap[child], _heap[parent]);
child = parent;
}
}
public T Dequeue()
{
if (Count == 0) throw new InvalidOperationException();
var result = _heap[0];
_heap[0] = _heap[Count - 1];
_heap.RemoveAt(Count - 1);
var parent = 0;
while (parent * 2 + 1 < Count)
{
var left = parent * 2 + 1;
var right = parent * 2 + 2;
if (right < Count && _comparison(_heap[left], _heap[right]) > 0)
left = right;
if (_comparison(_heap[parent], _heap[left]) <= 0) break;
(_heap[parent], _heap[left]) = (_heap[left], _heap[parent]);
parent = left;
}
return result;
}
public T Peek()
{
if (Count == 0) throw new InvalidOperationException();
return _heap[0];
}
public bool TryDequeue(out T result)
{
if (Count > 0)
{
result = Dequeue();
return true;
}
result = default;
return false;
}
public bool TryPeek(out T result)
{
if (Count > 0)
{
result = Peek();
return true;
}
result = default;
return false;
}
public void Clear() => _heap.Clear();
public bool Contains(T item) => _heap.Contains(item);
}
public static class Scanner
{
public static string ScanLine() => Console.ReadLine()?.Trim() ?? string.Empty;
public static string[] Scan() => ScanLine().Split(' ');
public static T Scan<T>() where T : IConvertible => Convert<T>(Scan()[0]);
public static (T1, T2) Scan<T1, T2>() where T1 : IConvertible where T2 : IConvertible
{
var line = Scan();
return (Convert<T1>(line[0]), Convert<T2>(line[1]));
}
public static (T1, T2, T3) Scan<T1, T2, T3>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible
{
var line = Scan();
return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]));
}
public static (T1, T2, T3, T4) Scan<T1, T2, T3, T4>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible
{
var line = Scan();
return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]));
}
public static (T1, T2, T3, T4, T5) Scan<T1, T2, T3, T4, T5>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible where T5 : IConvertible
{
var line = Scan();
return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]), Convert<T5>(line[4]));
}
public static (T1, T2, T3, T4, T5, T6) Scan<T1, T2, T3, T4, T5, T6>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible where T5 : IConvertible where T6 : IConvertible
{
var line = Scan();
return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]), Convert<T5>(line[4]), Convert<T6>(line[5]));
}
public static IEnumerable<T> ScanEnumerable<T>() where T : IConvertible => Scan().Select(Convert<T>);
private static T Convert<T>(string value) where T : IConvertible => (T)System.Convert.ChangeType(value, typeof(T));
}
}
}