import sys
sys.setrecursionlimit(10000)

def solve(s,k):
    if k == K: return True
    res = False
    for i in range(N):
        for c in G[s][i]:
            if c == d[k]:
                res = (solve(i,k+1) or res)
                if res: break
        if res: break
    return res

N,M,K = map(int,raw_input().split())
G = [[[] for _ in range(N)] for _ in range(N)]
for roop in range(M):
    a,b,c = map(int,raw_input().split())
    G[a-1][b-1].append(c);G[b-1][a-1].append(c)
d = map(int,raw_input().split())[::-1]

start = []
for s in range(N):
    if solve(s,0):
        start.append(s+1)
print len(start)
print " ".join(map(str,sorted(start)))