from collections import defaultdict

def elerheto(honnan, mostani):
    if mostani in beenThere:
        return
    kiElerheto.append(mostani)
    beenThere.append(mostani)
    if len(graf[mostani]) <= 2:
        if graf[mostani][0] != honnan:
            elerheto(mostani, graf[mostani][0])
        else:
            elerheto(mostani, graf[mostani][1])
    return

beenThere = []

n, m = list(map(int, input().split()))
graf = defaultdict(list)

kiElerheto = []
kiSzamlalo = 0


#todo Is there a way without array?
arr = [0 for i in range(n)]

for i in range(m):
    honnan1, hova = list(map(int, input().split()))

    graf[honnan1].append(hova)
    graf[hova].append(honnan1)

    arr[honnan1-1] += 1
    arr[hova-1] += 1

zsakfalvak = []
zsakfalvak = [i+1 for i, value in enumerate(arr) if value == 1]

for i in zsakfalvak:
    if len(graf[i]) == 1:
        elerheto(i, graf[i][0])


print(len(kiElerheto))
print(*sorted(kiElerheto))