#[doc = " https://github.com/hatoo/competitive-rust-snippets"]
#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};
#[allow(unused_imports)]
use std::iter::FromIterator;
#[allow(unused_macros)]
macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } }
#[macro_export]
macro_rules ! input { ( source = $ s : expr , $ ( $ r : tt ) * ) => { let mut parser = Parser :: from_str ( $ s ) ; input_inner ! { parser , $ ( $ r ) * } } ; ( parser = $ parser : ident , $ ( $ r : tt ) * ) => { input_inner ! { $ parser , $ ( $ r ) * } } ; ( new_stdin_parser = $ parser : ident , $ ( $ r : tt ) * ) => { let stdin = std :: io :: stdin ( ) ; let reader = std :: io :: BufReader :: new ( stdin . lock ( ) ) ; let mut $ parser = Parser :: new ( reader ) ; input_inner ! { $ parser , $ ( $ r ) * } } ; ( $ ( $ r : tt ) * ) => { input ! { new_stdin_parser = parser , $ ( $ r ) * } } ; }
#[macro_export]
macro_rules ! input_inner { ( $ parser : ident ) => { } ; ( $ parser : ident , ) => { } ; ( $ parser : ident , $ var : ident : $ t : tt $ ( $ r : tt ) * ) => { let $ var = read_value ! ( $ parser , $ t ) ; input_inner ! { $ parser $ ( $ r ) * } } ; }
#[macro_export]
macro_rules ! read_value { ( $ parser : ident , ( $ ( $ t : tt ) ,* ) ) => { ( $ ( read_value ! ( $ parser , $ t ) ) ,* ) } ; ( $ parser : ident , [ $ t : tt ; $ len : expr ] ) => { ( 0 ..$ len ) . map ( | _ | read_value ! ( $ parser , $ t ) ) . collect ::< Vec < _ >> ( ) } ; ( $ parser : ident , chars ) => { read_value ! ( $ parser , String ) . chars ( ) . collect ::< Vec < char >> ( ) } ; ( $ parser : ident , usize1 ) => { read_value ! ( $ parser , usize ) - 1 } ; ( $ parser : ident , $ t : ty ) => { $ parser . next ::<$ t > ( ) . expect ( "Parse error" ) } ; }
use std::io;
use std::io::BufRead;
use std::str;
pub struct Parser<R> {
    reader: R,
    buf: Vec<u8>,
    pos: usize,
}
impl Parser<io::Empty> {
    pub fn from_str(s: &str) -> Parser<io::Empty> {
        Parser {
            reader: io::empty(),
            buf: s.as_bytes().to_vec(),
            pos: 0,
        }
    }
}
impl<R: BufRead> Parser<R> {
    pub fn new(reader: R) -> Parser<R> {
        Parser {
            reader: reader,
            buf: vec![],
            pos: 0,
        }
    }
    pub fn update_buf(&mut self) {
        self.buf.clear();
        self.pos = 0;
        loop {
            let (len, complete) = {
                let buf2 = self.reader.fill_buf().unwrap();
                self.buf.extend_from_slice(buf2);
                let len = buf2.len();
                if len == 0 {
                    break;
                }
                (len, buf2[len - 1] <= 0x20)
            };
            self.reader.consume(len);
            if complete {
                break;
            }
        }
    }
    pub fn next<T: str::FromStr>(&mut self) -> Result<T, T::Err> {
        loop {
            let mut begin = self.pos;
            while begin < self.buf.len() && (self.buf[begin] <= 0x20) {
                begin += 1;
            }
            let mut end = begin;
            while end < self.buf.len() && (self.buf[end] > 0x20) {
                end += 1;
            }
            if begin != self.buf.len() {
                self.pos = end;
                return str::from_utf8(&self.buf[begin..end]).unwrap().parse::<T>();
            } else {
                self.update_buf();
            }
        }
    }
}
#[allow(unused_macros)]
macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } }
#[doc = " https://github.com/hatoo/competitive-rust-snippets"]
const BIG_STACK_SIZE: bool = true;
#[allow(dead_code)]
fn main() {
    use std::thread;
    if BIG_STACK_SIZE {
        thread::Builder::new()
            .stack_size(32 * 1024 * 1024)
            .name("solve".into())
            .spawn(solve)
            .unwrap()
            .join()
            .unwrap();
    } else {
        solve();
    }
}
fn solve() {
    input! {
        N: usize, M: usize,
        ABC: [(usize,usize,i64); M],
    }
    let mut g = vec![vec![]; N];
    let mut g_rev = vec![vec![]; N];
    for (a,b,c) in ABC.clone() {
        g[a-1].push(b-1);
        g_rev[b-1].push(a-1);
    }

    let mut used = vec![false; N];
    let mut q = VecDeque::new();
    q.push_back(0);
    used[0] = true;
    while !q.is_empty() {
        let u = q.pop_front().unwrap();
        for &v in &g[u] {
            if !used[v] {
                used[v] = true;
                q.push_back(v);
            }
        }
    }

    let mut used_rev = vec![false; N];
    let mut q = VecDeque::new();
    q.push_back(N-1);
    used_rev[N-1] = true;
    while !q.is_empty() {
        let u = q.pop_front().unwrap();
        for &v in &g_rev[u] {
            if !used_rev[v] {
                used_rev[v] = true;
                q.push_back(v);
            }
        }
    }

    let mut es = vec![];
    for (a,b,c) in ABC {
        let between_1N = used[a-1] && used[b-1] && used_rev[a-1] && used[b-1];
        if !between_1N { continue; }
        es.push(Edge{from:a-1,to:b-1,cost:-c});
    }
    
    if find_negative_loop(N, &es) {
        println!("inf");
        return
    }

    let dp = bellman_ford(N, &es, 0);
    println!("{}", -dp[N-1]);
}

    #[derive(Clone)]
    struct Edge {
        from: usize,
        to: usize,
        cost: i64, // can be negative
    }

    fn bellman_ford(n: usize, es: &[Edge], source: usize) -> Vec<i64> {
        const INF: i64 = 1<<60;
        let mut d = vec![INF; n];
        d[source] = 0;
        loop {
            let mut update = false;
            for e in es {
                if d[e.from] != INF && d[e.to] > d[e.from] + e.cost {
                    d[e.to] = d[e.from] + e.cost;
                    update = true;
                }
            }
            if !update {
                break;
            }
        }
        d
    }

    fn find_negative_loop(n: usize, es: &[Edge]) -> bool {
        let mut d = vec![0; n];
        for i in 0..n {
            for e in es {
                if d[e.to] > d[e.from] + e.cost {
                    d[e.to] = d[e.from] + e.cost;
                    if i == n - 1 {
                        return true;
                    }
                }
            }
        }
        false
    }

Measured memory_bytes: 8572