#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let N = input!(usize);
    let M = input!(usize);
    let A = input!(isize, N);

    let mut edges = vec![];

    for _ in 0..M {
        let a = input!(usize) - 1;
        let b = input!(usize) - 1;
        let c = input!(isize);

        edges.push((a, b, c - A[a]));
    }

    let ans = bellman_ford_algorithm(N, &edges, 0);

    if let Some(dist) = ans {
        writeln!(out, "{}", -dist[N - 1].unwrap() + A[N - 1]);
    } else {
        writeln!(out, "inf");
    }
}

pub fn bellman_ford_algorithm<
    W: Sized + std::ops::Add<Output = W> + PartialOrd + Ord + Default + Clone + Copy,
>(
    size: usize,
    directed_edges: &[(usize, usize, W)],
    start: usize,
) -> Option<Vec<Option<W>>> {
    assert!(start < size);

    let mut dist = vec![None; size];
    dist[start] = Some(W::default());

    for _ in 0..directed_edges.len() {
        for &(u, v, w) in directed_edges.iter() {
            let dv = dist[v];
            let du = dist[u];

            if let Some(du) = du {
                if let Some(dv) = dv {
                    if dv > du + w {
                        dist[v] = Some(du + w);
                    }
                } else {
                    dist[v] = Some(du + w);
                }
            }
        }
    }

    let dist_prev = dist.clone();

    for _ in 0..directed_edges.len() {
        for &(u, v, w) in directed_edges.iter() {
            let dv = dist[v];
            let du = dist[u];

            if let Some(du) = du {
                if let Some(dv) = dv {
                    if dv > du + w {
                        dist[v] = Some(du + w);
                    }
                } else {
                    dist[v] = Some(du + w);
                }
            }
        }
    }

    // 経路復元しながら頑張る?
    let mut now = size - 1;

    let mut graph = vec![vec![]; size];

    for &(u, v, w) in directed_edges {
        graph[v].push((u, w));
    }

    while now != start {
        let prev = now;

        for &(nxt, weight) in graph[now].iter() {
            if dist[now].is_some()
                && dist[nxt].is_some()
                && dist_prev[nxt] == dist[nxt]
                && dist_prev[now] == dist[now]
            {
                let d1 = dist[now].unwrap();
                let d2 = dist[nxt].unwrap();

                if d1 == d2 + weight {
                    now = nxt;
                    break;
                }
            }
        }

        if prev == now {
            return None;
        }
    }

    return Some(dist);
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}