macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

fn main() {
    input! {
    n: usize,
        m: usize,
        abc: [(usize, usize, i64); m],
    }
    let mut graph = Graph::new(n);
    for i in 0..m {
        let (a, b, c) = abc[i];
        graph.add_costs(a-1, b-1, -1 * c, true);
    }
    let (negative, d) = graph.bellmanford_search_negative_cycle(0);
    //println!("{:?}, {}", d, negative);
    if negative || d[n-1] == INF {
        println!("{}", "inf");
    } else {
        println!("{}", -1 * d[n-1]);
    }
}

const INF: i64 = 1 << 61;

struct Graph {
    edges: Vec<(usize, usize, i64)>, // adjacent list
    n: usize
}

impl Graph {
    fn new(n: usize) -> Self {
        Graph {
            edges: vec![],
            n: n
        }
    }

    fn add_costs(&mut self, from: usize, to: usize, cost: i64, directed: bool) {
        if directed {
            self.edges.push((from, to, cost));
        } else {
            self.edges.push((from, to, cost));
            self.edges.push((to, from, cost));
        }
    }

    fn bellmanford_search(&self, start: usize) -> Vec<i64> {
        const INF: i64 = 1 << 61;
        let mut dist: Vec<i64> = vec![INF; self.n];
        dist[start] = 0;
        loop {
            let mut update: bool = false;
            for edge in &self.edges {
                let (from, to, cost) = *edge;
                if (dist[from] != INF) & (dist[to] > dist[from] + cost) {
                    dist[to] = dist[from] + cost;
                    update = true;
                }
            }
            if !update {
                break;
            }
        }
        return dist
    }

    fn bellmanford_search_negative_cycle(&self, start: usize) -> (bool, Vec<i64>) {
        // (true, dist) なら負の閉路を含む
        let mut dist: Vec<i64> = vec![INF; self.n];
        dist[start] = 0;
        for i in 0..self.n {
            for &(from, to, cost) in &self.edges{
                if (dist[from] != INF) & (dist[to] > dist[from] + cost) {
                    dist[to] = dist[from] + cost;
                    if i == self.n - 1 && to == self.n-1 {
                        return (true, dist);
                    }
                }
            }
        }
        return (false, dist);
    }
}

Measured memory_bytes: 4352