from collections import defaultdict

tole = 0
elozo = ""

ki = []

def szomszed(froma):
    global tole
    global elozo
    if (len(graf[froma])) < 3:
        #print(froma)
        tole += 1
        if graf[froma][0] == elozo:
            ki.append(froma)
            elozo = froma
            return szomszed(graf[froma][1])
        else:
            return szomszed(graf[froma][0])
    ki.append(froma)
    return 0

n, m = list(map(int, input().split()))
graf = defaultdict(list)
arr = [0 for i in range(n)]

for i in range(m):
    honnan, hova = list(map(int, input().split()))
    graf[honnan].append(hova)
    graf[hova].append(honnan)
    arr[honnan-1] += 1
    arr[hova-1] += 1

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

asd = 0

for i in zsakfalvak:
    elozo = i
    szomszed(i)
    asd += tole
    tole = 0

print(asd)
print(*ki.sort())