uu帮忙看看最后一题， from collections import defaultdict nodes = defaultdict(list) n, a, b, m = map(int, input().split()) roots = list(map(int, input().split())) for i, x in enumerate(roots): nodes[x].append(i+2) def dfs(i): if len(nodes[i]) == 0: return 0 t = 0 for nx in nodes[i]: t += (dfs(nx) % m + a**i % m) * b % m return t % m print(dfs(1))