import sys
sys.setrecursionlimit(505050)

def bridge(G, N):  # from https://tjkendev.github.io/procon-library/python/graph/bridge.html
    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)]
d = {}
for i in range(1, N+1):
    a, b = map(int, input().split())
    if a > b:
        a, b = b, a
    a -= 1
    b -= 1
    G[a].append(b)
    G[b].append(a)
    d[(a, b)] = i

ans = bridge(G, N)
print(N - len(ans))
for a in ans:
    del d[a]
print(" ".join(map(str, d.values())))