def main():
  N,M=map(int,input().split())
  V=[0]*N
  ans=[]
  for i in range(M):
    u,v=map(int,input().split())
    u-=1
    v-=1
    if V[u]==0 and V[v]==0:
      V[u]=1
      V[v]=1
      ans.append(i+1)
  print(len(ans))
  for i in ans:
    print(i)
  return

main()