import sys
sys.setrecursionlimit(50000000)

def read(): return sys.stdin.readline().strip()
def read_int(): return int(read())
def read_ints(): return map(int, read().split())

def buildtr(u, pre):
    size[u] = 1
    for v in link[u]:
        if v == pre: continue
        buildtr(v, u)
        size[u] += size[v]
        f[u] += f[v]
    f[u] += size[u]
def dfsdye(u, pre):
    global ans
    if u != 1:
        f[u] = f[pre] + n - 2 * size[u]
        ans = max(ans, f[u])
    for v in link[u]:
        if v == pre: continue
        dfsdye(v, u)

n = read_int()
link = [[] for _ in range(n + 1)]
for i in range(n - 1):
    u, v = read_ints()
    link[u].append(v)
    link[v].append(u)
size = [0] * (n + 1)
f = [0] * (n + 1)
buildtr(1, 0)
ans = f[1]
dfsdye(1, 0)
print(ans)

原站给的信息是#1~#29 AC，#30 RE。但是我找不到问题出在哪了qaq，求助