from collections import defaultdict

def elerheto(honnan, mostani):

    if mostani not in kiElerheto:
    
        kiElerheto.add(mostani)
        if len(graf[mostani]) == 2:
            if graf[mostani][0] != honnan:
                return elerheto(mostani, graf[mostani][0])
            else:
                return elerheto(mostani, graf[mostani][1])
        
        return
    else:
        return 0


beenThere = []

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

kiElerheto = set()
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(*(kiElerheto))