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);
        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)>();
        foreach (var edge in map)
        {
            tree[edge[0] - 1].Add((edge[1] - 1, edge[2] - a[edge[1] - 1]));
        }
        var INF = long.MaxValue / 2;
        var len = Enumerable.Repeat(INF, n).ToArray();
        len[0] = -a[0];
        var ans = 0L;
        var ans2 = 0L;
        for (var i = 0; i < 2 * n; ++i)
        {
            for (var j = 0; j < n; ++j) foreach (var next in tree[j]) len[next.to] = Math.Min(len[next.to], len[j] + next.len);
            if (i + 1 == n) ans = len[n - 1];
            if (i + 1 == 2 * n) ans2 = len[n - 1];
        }
        WriteLine(ans != ans2 ? "inf" : (-ans).ToString());
    }
}