use std::io::Write;
use std::collections::*;

type Map<K, V> = BTreeMap<K, V>;
type Set<T> = BTreeSet<T>;
type Deque<T> = VecDeque<T>;

fn main() {
    input! {
        n: usize,
        m: usize,
        e: [(usize1, usize1, i32); m],
    }
    let mut e = e;
    for e in e.iter_mut() {
        *e = (e.0.min(e.1), e.0.max(e.1), e.2);
    }
    e.sort_by_key(|e| e.2);
    let mut g = vec![vec![]; n];
    for &(a, b, c) in e.iter() {
        g[a].push((a, b, c));
        g[b].push((a, b, c));
    }
    let mut dsu = DSU::new(n);
    let mut tree = vec![vec![]; n];
    let mut val = std::i32::MAX;
    let mut ans = std::i32::MAX;
    for (a, b, c) in e {
        if (a, b) == (0, n - 1) {
            ans.chmin(c);
        }
        if let Some((p, ch)) = dsu.unite(a, b) {
            tree[a].push((b, c));
            tree[b].push((a, c));
            let x = std::mem::take(&mut g[ch]);
            for (a, b, c) in x {
                if dsu.same(a, b) {
                    continue;
                }
                g[p].push((a, b, c));
                let mut p = [dsu.root(0), dsu.root(n - 1)];
                let mut q = [dsu.root(a), dsu.root(b)];
                p.sort();
                q.sort();
                if p == q {
                    val.chmin(c);
                }
            }
        }
        if val < std::i32::MAX {
            ans.chmin(c + val);
        }
    }
    let mut dfs = vec![0];
    let mut parent = vec![(n, 0); n];
    parent[0].0 = 0;
    while let Some(v) = dfs.pop() {
        for &(u, w) in tree[v].iter() {
            if parent[u].0 == n {
                parent[u] = (v, w);
                dfs.push(u);
            }
        }
    }
    let mut a = vec![];
    let mut pos = n - 1;
    while pos != 0 {
        let p = parent[pos];
        a.push(p.1);
        pos = p.0;
    }
    a.sort();
    ans.chmin(a.iter().rev().take(2).sum::<i32>());
    println!("{}", ans);
}

// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------
//---------- begin union_find ----------
pub struct DSU {
    p: Vec<i32>,
}
impl DSU {
    pub fn new(n: usize) -> DSU {
        assert!(n < std::i32::MAX as usize);
        DSU { p: vec![-1; n] }
    }
    pub fn init(&mut self) {
        self.p.iter_mut().for_each(|p| *p = -1);
    }
    pub fn root(&self, mut x: usize) -> usize {
        assert!(x < self.p.len());
        while self.p[x] >= 0 {
            x = self.p[x] as usize;
        }
        x
    }
    pub fn same(&self, x: usize, y: usize) -> bool {
        assert!(x < self.p.len() && y < self.p.len());
        self.root(x) == self.root(y)
    }
    pub fn unite(&mut self, x: usize, y: usize) -> Option<(usize, usize)> {
        assert!(x < self.p.len() && y < self.p.len());
        let mut x = self.root(x);
        let mut y = self.root(y);
        if x == y {
            return None;
        }
        if self.p[x] > self.p[y] {
            std::mem::swap(&mut x, &mut y);
        }
        self.p[x] += self.p[y];
        self.p[y] = x as i32;
        Some((x, y))
    }
    pub fn parent(&self, x: usize) -> Option<usize> {
        assert!(x < self.p.len());
        let p = self.p[x];
        if p >= 0 {
            Some(p as usize)
        } else {
            None
        }
    }
    pub fn sum<F>(&self, mut x: usize, mut f: F) -> usize
    where
        F: FnMut(usize),
    {
        while let Some(p) = self.parent(x) {
            f(x);
            x = p;
        }
        x
    }
    pub fn size(&self, x: usize) -> usize {
        assert!(x < self.p.len());
        let r = self.root(x);
        (-self.p[r]) as usize
    }
}
//---------- end union_find ----------
// ---------- begin chmin, chmax ----------
pub trait ChangeMinMax {
    fn chmin(&mut self, x: Self) -> bool;
    fn chmax(&mut self, x: Self) -> bool;
}

impl<T: PartialOrd> ChangeMinMax for T {
    fn chmin(&mut self, x: Self) -> bool {
        *self > x && {
            *self = x;
            true
        }
    }
    fn chmax(&mut self, x: Self) -> bool {
        *self < x && {
            *self = x;
            true
        }
    }
}
// ---------- end chmin, chmax ----------