mod = 1000000007
eps = 10**-9
inf = 10**18


def main():
    import sys
    from collections import deque
    input = sys.stdin.buffer.readline

    N, Q, C = map(int, input().split())
    adj = [[] for _ in range(N+1)]
    for _ in range(N-1):
        a, b, c = map(int, input().split())
        adj[a].append((b, c))
        adj[b].append((a, c))
    X = list(map(int, input().split()))

    dp = [inf] * (N+1)
    dp[X[0]] = 0
    for i in range(Q-1):
        u0 = X[i]
        v0 = X[i+1]
        que = deque()
        que.append(v0)
        seen = [-1] * (N+1)
        seen[v0] = 0
        par = [0] * (N+1)
        child = [[] for _ in range(N+1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u, c in adj[v]:
                if seen[u] == -1:
                    seen[u] = seen[v] + c
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()

        dp_new = [inf] * (N+1)
        dp_tree = [inf] * (N+1)
        for j in range(1, N+1):
            if dp[j] == inf:
                continue
            dp_new[j] = dp[j] + seen[u0]
            dp_tree[u0] = min(dp_tree[u0], dp[j] + seen[u0])
            dp_tree[j] = min(dp_tree[j], dp[j] + C + seen[j])
        for v in seq:
            for u in child[v]:
                dp_tree[v] = min(dp_tree[v], dp_tree[u])
            dp_new[v] = min(dp_new[v], dp_tree[v])
        dp = dp_new
    print(min(dp))


if __name__ == '__main__':
    main()