import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum E = 13;
enum INF = 10L^^18;

int N, Q;
long C;
int[] A, B;
long[] L;
int[] X;

int[][] G;
long[] dep;
int[] poss;
alias Entry = Tuple!(long, "d", int, "u");
Entry[] es;
void dfs(int u, int p, long d) {
  dep[u] = d;
  poss[u] = cast(int)(es.length);
  es ~= Entry(d, u);
  foreach (i; G[u]) {
    const v = A[i] ^ B[i] ^ u;
    if (v != p) {
      dfs(v, u, d + L[i]);
      es ~= Entry(d, u);
    }
  }
}

int esLen;
Entry[][] mns;
int lca(int u, int v) {
  int a = poss[u], b = poss[v];
  if (a > b) {
    swap(a, b);
  }
  const e = bsr(b - a + 1);
  const l = min(mns[e][a], mns[e][b + 1 - (1 << e)]).u;
  debug {
    // writefln("lca %s %s = %s", u, v, l);
  }
  return l;
}

long[] shortest(long[] ini) {
  alias Node = Tuple!(long, "c", int, "u");
  BinaryHeap!(Array!Node, "a > b") que;
  auto ds = ini.dup;
  foreach (u; 0 .. N) {
    que.insert(Node(ds[u], u));
  }
  for (; !que.empty; ) {
    const c = que.front.c;
    const u = que.front.u;
    que.removeFront;
    if (ds[u] == c) {
      foreach (i; G[u]) {
        const v = A[i] ^ B[i] ^ u;
        const cc = c + L[i];
        if (chmin(ds[v], cc)) {
          que.insert(Node(cc, v));
        }
      }
    }
  }
  return ds;
}

void main() {
  try {
    for (; ; ) {
      N = readInt();
      Q = readInt();
      C = readLong();
      A = new int[N - 1];
      B = new int[N - 1];
      L = new long[N - 1];
      foreach (i; 0 .. N - 1) {
        A[i] = readInt() - 1;
        B[i] = readInt() - 1;
        L[i] = readLong();
      }
      X = new int[Q];
      foreach (q; 0 .. Q) {
        X[q] = readInt() - 1;
      }
      
      G = new int[][N];
      foreach (i; 0 .. N - 1) {
        G[A[i]] ~= i;
        G[B[i]] ~= i;
      }
      
      auto dist = new long[][](N, N);
      foreach (u; 0 .. N) {
        auto ini = new long[N];
        ini[] = INF;
        ini[u] = 0;
        dist[u] = shortest(ini);
      }
      
      auto dp = new long[][](Q, N);
      foreach (q; 0 .. Q) {
        dp[q][] = INF;
      }
      dp[0][X[0]] = 0;
      foreach (q; 0 .. Q - 1) {
        foreach (u; 0 .. N) {
          chmin(dp[q + 1][u], dp[q][u] + dist[X[q]][X[q + 1]]);
        }
        auto ini = dp[q].dup;
        ini[] += C;
        chmin(ini[X[q]], dp[q].minElement);
        const res = shortest(ini);
        foreach (u; 0 .. N) {
          chmin(dp[q + 1][u], res[u] + dist[u][X[q + 1]]);
        }
      }
      debug {
        foreach (q; 0 .. Q) {
          writeln(dp[q]);
        }
      }
      const ans = dp[Q - 1].minElement;
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}