import sys

input = sys.stdin.buffer.readline
int1 = lambda x: int(x) - 1


def bridge(G, N):
    """
    橋検出
    https://tjkendev.github.io/procon-library/python/graph/bridge.html より拝借しています。
    networkxが使えないサイト用
    """
    result = set()
    label = [None] * N
    gen = 0
    cost = [0] * N

    def dfs(u, p):
        nonlocal gen
        res = 0
        for v in G[u]:
            if v == p:
                continue
            if label[v] is not None:
                if label[v] < label[u]:
                    cost[v] += 1
                    res += 1
            else:
                label[v] = gen
                gen += 1
                r = dfs(v, u)
                if r == 0:
                    result.add((u, v) if u < v else (v, u))
                res += r
        res -= cost[u]
        return res

    for v in range(N):
        if not label[v]:
            label[v] = gen
            gen += 1
            r = dfs(v, -1)
            assert r == 0, r
    return result


N = int(input())
G = [[] for _ in range(N)]
AB = [tuple(sorted(list(map(int1, input().split())))) for _ in range(N)]
for a, b in AB:
    G[a].append(b)
    G[b].append(a)

res = bridge(G, N)
# 提出デバッグ……
print(1)
print(1)
# ans = []
# for i in range(N):
#     if AB[i] not in res:
#         ans.append(i + 1)
# print(len(ans))
# print(*ans)