using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var a = NList;
        var map = NArr(m);
        WriteLine(Play(n, m, a, map));
    }
    static string Play(int n, int m, int[] a, int[][] map)
    {
        var tree = new List<(int to, long len)>[n];
        for (var i = 0; i < tree.Length; ++i) tree[i] = new List<(int to, long len)>();
        var revtree = new List<int>[n];
        for (var i = 0; i < revtree.Length; ++i) revtree[i] = new List<int>();
        foreach (var edge in map)
        {
            tree[edge[0] - 1].Add((edge[1] - 1, a[edge[1] - 1] - edge[2]));
            revtree[edge[1] - 1].Add(edge[0]);
        }
        var reachable = new bool[n];
        DFS(n - 1, revtree, reachable);
        var INF = long.MinValue / 2;
        var len = Enumerable.Repeat(INF, n).ToArray();
        len[0] = a[0];
        for (var i = 0; i < n; ++i)
        {
            var flg = false;
            for (var j = 0; j < n; ++j) foreach (var next in tree[j])
            {
                if (len[next.to] < len[j] + next.len)
                {
                    if (reachable[next.to]) flg = true;
                    len[next.to] = len[j] + next.len;
                }
            }
            if (i + 1 == n && flg)
            {
                return "inf";
            }
        }
        return len[^1].ToString();
    }
    static void DFS(int cur, List<int>[] tree, bool[] reachable)
    {
        reachable[cur] = true;
        foreach (var next in tree[cur])
        {
            if (reachable[next]) continue;
            DFS(next, tree, reachable);
        }
    }
}