from sys import stdin
def main():
    N, M = [int(i) for i in input().split()]

    K = [[] for i in range(N+1)]

    for i in range(M): #kapcsolatok boelvasása
        x,y = [int(i) for i in stdin.readline().split()]
        K[x].append(y)
        K[y].append(x)
        
    Z = [i for i,s in enumerate(K) if len(s)==1] #zsákfalvak kiválasztása

    S = []
    for z in Z:
        R = z
        P = K[z][:]
        while len(P) == 1:
            P = P[0]
            if P not in S:
                S.append(P)
            i = P
            P = K[P][:]
            P.remove(R)
            R = i
            
    print(len(S))
    S.sort()
    print(*S)
main()