#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($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, [ $t:tt ]) => {{
        let len = read_value!($next, usize);
        read_value!($next, [$t; len])
    }};
    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
}

pub struct LCA {
    st: Vec<usize>,
    par: Vec<usize>,
    jmp: Vec<usize>,
    dep: Vec<usize>,
}

// Constant-factor speedup used in https://codeforces.com/contest/1083/submission/46874242.
// Base on HL-decomposition.
// par[root] = root should hold.
// These functions use O(n) stack space.
// Verified by https://codeforces.com/contest/1083/submission/51934575.
impl LCA {
    // For each node, make the most heavy child the first child.
    fn dfs_left(ch: &mut [Vec<usize>], v: usize, sz: &mut [usize],
                dep: &mut [usize], d: usize) {
        dep[v] = d;
        let mut s = 1;
        for i in 0..ch[v].len() {
            let w = ch[v][i];
            Self::dfs_left(ch, w, sz, dep, d + 1);
            s += sz[w];
            if sz[w] > sz[ch[v][0]] {
                ch[v].swap(i, 0);
            }
        }
        sz[v] = s;
    }
    fn dfs(ch: &[Vec<usize>], st: &mut [usize], v: usize,
           cnt: &mut usize, jmp: &mut [usize]) {
        st[v] = *cnt;
        *cnt += 1;
        if ch[v].len() >= 1 {
            jmp[ch[v][0]] = jmp[v];
        }
        for &w in &ch[v] {
            Self::dfs(ch, st, w, cnt, jmp);
        }
    }
    pub fn new(ch: &mut [Vec<usize>], par: &[usize], root: usize) -> Self {
        let n = ch.len();
        let mut st = vec![0; n];
        let mut cnt = 0;
        let mut sz = vec![0; n];
        let mut jmp = vec![0; n];
        let mut dep = vec![0; n];
        Self::dfs_left(ch, root, &mut sz, &mut dep, 0);
        for i in 0..n {
            jmp[i] = i;
        }
        Self::dfs(ch, &mut st, root, &mut cnt, &mut jmp);
        LCA {
            st: st,
            par: par.to_vec(),
            jmp: jmp,
            dep: dep,
        }
    }
    pub fn lca(&self, mut x: usize, mut y: usize) -> usize {
        let jmp = &self.jmp;
        let st = &self.st;
        while jmp[x] != jmp[y] {
            if st[x] < st[y] {
                std::mem::swap(&mut x, &mut y);
            }
            x = self.par[jmp[x]];
        }
        if st[x] < st[y] {
            x
        } else {
            y
        }
    }
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}

fn dfs(v: usize, par: usize, g: &[Vec<(usize, i64)>], ch: &mut [Vec<usize>], pars: &mut [usize], dist: &mut [i64], d: i64) {
    dist[v] = d;
    for &(w, c) in &g[v] {
        if w == par {
            pars[v] = w;
            continue;
        }
        ch[v].push(w);
        dfs(w, v, g, ch, pars, dist, d + c);
    }
}

fn solve() {
    input! {
        n: usize, q: usize, c: i64,
        uvl: [(usize1, usize1, i64); n - 1],
        x: [usize1; q],
    }
    let mut g = vec![vec![]; n];
    for (u, v, l) in uvl {
        g[u].push((v, l));
        g[v].push((u, l));
    }
    let mut ch = vec![vec![]; n];
    let mut pars = vec![0; n];
    let mut dist = vec![0; n];
    dfs(0, n, &g, &mut ch, &mut pars, &mut dist, 0);
    let lca = LCA::new(&mut ch, &pars, 0);
    const INF: i64 = 1 << 60;
    let mut dp = vec![INF; n];
    let mut dpn = 0;
    for i in 1..q {
        let mut ep = vec![INF; n];
        let mut epn = INF;
        let mut que = BinaryHeap::new();
        for i in 0..n {
            que.push((Reverse(dp[i]), i));
        }
        que.push((Reverse(dpn - c), x[i - 1]));
        while let Some((Reverse(d), v)) = que.pop() {
            if ep[v] <= d { continue; }
            ep[v] = d;
            for &(w, c) in &g[v] {
                que.push((Reverse(d + c), w));
            }
        }
        let mut dist = vec![INF; n];
        let mut que = VecDeque::new();
        que.push_back((0, x[i]));
        while let Some((d, v)) = que.pop_front() {
            if dist[v] <= d { continue; }
            dist[v] = d;
            for &(w, c) in &g[v] {
                que.push_back((d + c, w));
            }
        }
        for i in 0..n {
            ep[i] += c + dist[i];
            epn = min(epn, dp[i] + c + dist[i]);
        }
        let distx = dist[x[i - 1]];
        epn = min(epn, dpn + distx);
        for i in 0..n {
            ep[i] = min(ep[i], dp[i] + distx);
        }
        dp = ep;
        dpn = epn;
        // eprintln!("{:?} {}", dp, dpn);
    }
    println!("{}", dpn);
}