N, M = map(int, input().split())
ans = []
s = set()
for i in range(M):
    u, v = map(int, input().split())
    if not u in s and not v in s:
        ans.append(i + 1)
        s.add(u)
        s.add(v)

print(len(ans))
print(*ans, sep="\n")