class Graph:
    #入力定義
    def __init__(self,vertex=[]):
        self.vertex=set(vertex)

        self.edge_number=0
        self.adjacent={v:set() for v in vertex}

    #頂点の追加
    def add_vertex(self,*adder):
        for v in adder:
            if not self.vertex_exist(v):
                self.adjacent[v]=set()
                self.vertex.add(v)

    #辺の追加
    def add_edge(self,u,v):
        self.add_vertex(u)
        self.add_vertex(v)

        if not self.edge_exist(u,v):
            self.adjacent[u].add(v)
            self.adjacent[v].add(u)
            self.edge_number+=1

    #辺を除く
    def remove_edge(self,u,v):
        self.add_vertex(u)
        self.add_vertex(v)

        if self.edge_exist(u,v):
            self.adjacent[u].discard(v)
            self.adjacent[v].discard(u)
            self.edge_number-=1

    #頂点を除く
    def remove_vertex(self,*vertexes):
        for v in vertexes:
            if self.vertex_exist(v):
                U=self.neighbohood(v)
                for u in U:
                    self.edge_number-=1
                    self.adjacent[u].discard(v)

                del self.adjacent[v]
                self.vertex.discard(v)

    #Walkの追加
    def add_walk(self,*walk):
        n=len(walk)
        for i in range(n-1):
            self.add_edge(walk[i],walk[i+1])

    #Cycleの追加
    def add_cycle(self,*cycle):
        self.add_walk(*cycle)
        self.add_edge(cycle[-1],cycle[0])

    #頂点の交換
    def __vertex_swap(self,p,q):
        self.vertex.sort()

    #グラフに頂点が存在するか否か
    def vertex_exist(self,v):
        return v in self.vertex

    #グラフに辺が存在するか否か
    def edge_exist(self,u,v):
        if not(self.vertex_exist(u) and self.vertex_exist(v)):
            return False
        return v in self.adjacent[u]

    #近傍
    def neighbohood(self,v):
        if not self.vertex_exist(v):
            return []
        return list(self.adjacent[v])

    #次数
    def degree(self,v):
        if not self.vertex_exist(v):
            return 0

        return len(self.adjacent[v])

    #頂点数
    def vertex_count(self):
        return len(self.vertex)

    #辺数
    def edge_count(self):
        return self.edge_number

    #頂点vを含む連結成分
    def connected_component(self,v):
        if v not in self.adjacent:
            return []

        from collections import deque
        T={u:0 for u in self.vertex}
        T[v]=1
        Q=deque([v])
        while Q:
            u=Q.popleft()
            for w in self.adjacent[u]:
                if not T[w]:
                    T[w]=1
                    Q.append(w)
        return [x for x in self.adjacent if T[x]]

    #距離
    def distance(self,u,v):
        from collections import deque
        inf=float("inf")
        T={v:inf  for v in self.vertex}

        if u==v:
            return 0
        Q=deque([u])
        T[u]=0
        while Q:
            w=Q.popleft()
            for x in self.adjacent[w]:
                if T[x]==inf:
                    T[x]=T[w]+1
                    Q.append(x)
                    if x==v:
                        return T[x]
        return inf

    #ある1点からの距離
    def distance_all(self,u):
        from collections import deque
        inf=float("inf")
        T={v:inf  for v in self.vertex}

        Q=deque([u])
        T[u]=0
        while Q:
            w=Q.popleft()
            for x in self.adjacent[w]:
                if T[x]==inf:
                    T[x]=T[w]+1
                    Q.append(x)
        return T

    #最短路
    def shortest_path(self,u,v):
        from collections import deque
        inf=float("inf")
        T={v:None for v in self.vertex}

        if u==v:
            return [u]

        Q=deque([u])
        T[u]=u
        while Q:
            w=Q.popleft()
            for x in self.adjacent[w]:
                if not T[x]:
                    T[x]=w
                    Q.append(x)
                    if x==v:
                        P=[v]
                        a=v
                        while a!=u:
                            a=T[a]
                            P.append(a)
                        return P[::-1]
        return None

    #何かしらの頂点を選ぶ.
    def poping_vertex(self):
        v=self.vertex.pop()
        self.vertex.add(v)
        return v

def Bridge(G):
    from collections import deque

    B=[]
    ord={v:-1 for v in G.vertex}
    flag={v:0 for v in G.vertex}
    nei=G.adjacent

    #BFSパート
    for v in G.vertex:
        if flag[v]:
            continue

        k=0
        parent={}
        S=deque([v])
        T=[]
        X=[]

        while S:
            u=S.pop()
            if flag[u]:
                continue

            T.append(u)
            ord[u]=k
            k+=1
            flag[u]=1

            if u!=v:
                X.append((parent[u],u))

            for w in nei[u]:
                if not flag[w]:
                    S.append(w)
                    parent[w]=u

        low={v:ord[v] for v in T}
        for w in T[:0:-1]:
            for x in nei[w]:
                if w==v or x!=parent[w]:
                    low[w]=min(low[w],low[x],ord[x])

        for u,w in X:
            if ord[u]<low[w]:
                B.append((u,w))
        return B
#================================================
import sys
input=sys.stdin.readline
write=sys.stdout.write

N=int(input())
G=Graph(range(1,N+1))
E={}

for i in range(1,N+1):
    a,b=map(int,input().split())

    if a>b:
        a,b=b,a

    G.add_edge(a,b)
    E[(a,b)]=i

B=set([(min(*p),max(*p)) for p in Bridge(G)])
T=[E[p] for p in E if p not in B]

print(len(T))
write(" ".join(map(str,T)))