import sys

# sys.setrecursionlimit(1000005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

n,q,c=LI()
to=[[] for _ in range(n)]
for _ in range(n-1):
    u,v,l=LI1()
    l+=1
    to[u].append((v,l))
    to[v].append((u,l))
xx=LI1()

def dfs(root=0):
    uu, stack = [], [root]
    while stack:
        u = stack.pop()
        uu.append(u)
        for v,l in to[u]:
            if v == parent[u]: continue
            parent[v] = u
            depth[v] = depth[u]+l
            stack.append(v)
    return uu

dp=[inf]*n
dp[xx[0]]=0
for s,t in zip(xx,xx[1:]):
    dp,pre=[inf]*n,dp
    parent, depth = [-1]*n, [0]*n
    uu = dfs(t)
    for u in uu[::-1]:
        dp[u] = min(dp[u], pre[u]+depth[u]+c,pre[u]+depth[s])
        if u==s:dp[u]=min(dp[u],min(pre)+depth[s])
        if u==t:break
        p=parent[u]
        dp[p]=min(dp[p],dp[u])
    # print(t,dp)

print(min(dp))