use proconio::{input, marker::Usize1};

fn main() {
    input! {
        n:usize,
        m:usize,
        a:[i64;n],
        abc:[(Usize1,Usize1,i64);m],
    }

    let mut g = vec![vec![]; n];
    let mut rg = vec![vec![]; n];
    for &(u, v, w) in abc.iter() {
        if u != n - 1 && v != n - 1 {
            g[u].push((v, w - a[u]));
        }
        rg[v].push(u);
    }

    let mut vis = vec![false; n];
    f(n - 1, &mut vis, &rg);

    const INF: i64 = std::i64::MAX;
    let mut dists = vec![INF; n];
    dists[0] = 0;
    for i in 1..=n {
        for j in 0..n {
            for &(k, w) in g[j].iter() {
                if !vis[j] || !vis[k] {
                    continue;
                }
                if dists[j] != INF && dists[k] > dists[j] + w {
                    dists[k] = dists[j] + w;

                    if i == n {
                        println!("inf");
                        return;
                    }
                }
            }
        }
    }

    let ans = -abc
        .iter()
        .filter(|&&(_, v, _)| v == n - 1)
        .map(|&(u, v, w)| dists[u] + w - a[u] - a[v])
        .min()
        .unwrap();

    println!("{}", ans);
}

fn f(crr: usize, vis: &mut Vec<bool>, g: &Vec<Vec<usize>>) {
    vis[crr] = true;
    for &nxt in g[crr].iter() {
        if vis[nxt] {
            continue;
        }

        f(nxt, vis, g);
    }
}