n,m=map(int,input().split())
A=set()
Ans=[]
for i in range(1,m+1):
	a,b=map(int,input().split())
	if not a in A and not b in A:
		Ans.append(i)
		A.add(a)
		A.add(b)
print(len(Ans))
for i in Ans:
	print(i)