from sys import stdin

def main():
    N,M = [int(i) for i in input().split()]
    U = [[] for i in range(N+1)]
    for i in range(M):
        a,b = [int(i) for i in stdin.readline().split()]
        U[a].append(b)
        U[b].append(a)

    zsak = [i for i in range(1,N+1) if len(U[i]) == 1]

    ent = []   # elágazás nélküli települések
    for zs in zsak:
        z = zs
        ut = U[z][:]
        while len(ut) == 1:
            falu = ut[0]
            if falu not in ent:
                ent.append(falu)
            ut = U[falu][:]
            ut.remove(z)
            z = falu

    print(len(ent))
    if ent != []:
        ent.sort()
        print(*ent)
main()