N = int(input())

sor = []
for i in range(N):
    s = list(map(int, input().split(' ')))
    sor += [s[0]]
    sor += [s[1]]

#print(sor)

pre = [0]*N
for i in range(len(sor)):
    pre[sor[i]-1] += 1

marad = []
for i in range(len(pre)):
    if pre[i] < 2:
        marad += [i]

for i in range(2**N, 2**(N+1)):
    
    v = bin(i)[3:]
    j = 0
    while j < len(marad) and v[marad[j]] == '0':
        j += 1
       
    if j == len(marad) and v.count('1') > 1:
        pre = [0]*N
        for k in range(len(v)):
            if v[k] =='1':
                pre[sor[k*2]-1] += 1
                pre[sor[k*2+1]-1] += 1
        #print(v, pre, v.count('1'))
        v2, h = '', []
        for i in range(len(pre)):
            if pre[i] > 1:
                v2 += '1'
                h += [i+1]
            else:
                v2 += '0'
        #print(v, v2)
        if v == v2:
            
            print(len(h))
            print(' '.join(list(map(str, h))))