// ---------- begin chmin, chmax ----------
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 ----------
// ---------- begin input macro ----------
// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
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_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_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 ----------

fn dijkstra(s: usize, t: usize, g: &[Vec<(usize, i64, usize)>], m: usize) -> (i64, Vec<Option<(usize, usize)>>) {
    let mut dp = vec![(std::i64::MAX, 0, 0); g.len()];
    dp[s] = (0, s, 0);
    let mut h = std::collections::BinaryHeap::new();
    h.push((0, s));
    while let Some((d, v)) = h.pop() {
        let d = -d;
        if d > dp[v].0 {
            continue;
        }
        for &(u, c, k) in g[v].iter() {
            let d = d + c;
            if dp[u].chmin((d, v, k)) {
                h.push((-d, u));
            }
        }
    }
    let mut used = vec![None; m];
    let mut pos = t;
    while pos != s {
        let (_, p, k) = dp[pos];
        used[k] = Some((p, pos));
        pos = p;
    }
    (dp[t].0, used)
}

fn run() {
    input! {
        n: usize,
        m: usize,
        e: [(usize1, usize1, i64, i64); m],
    }
    let mut g = vec![vec![]; n];
    for (i, &(a, b, c, _)) in e.iter().enumerate() {
        g[a].push((b, c, i));
        g[b].push((a, c, i));
    }
    let mut ans = 0;
    let (d, used) = dijkstra(0, n - 1, &g, m);
    ans += d;
    let mut g = vec![vec![]; n];
    for (i, (used, &(a, b, c, d))) in used.iter().zip(e.iter()).enumerate() {
        if let Some((p, q)) = *used {
            g[p].push((q, d, i));
            g[q].push((p, -c, i));
        } else {
            g[a].push((b, c, i));
            g[b].push((a, c, i));
        }
    }
    ans += dijkstra(0, n - 1, &g, m).0;
    println!("{}", ans);
}

fn main() {
    run();
}