import sys
input = sys.stdin.readline
N, M = map(int, input().split())
G = [[] for _ in range(N)]
ans = []
for i in range(M):
    u, v = map(int, input().split())
    u-=1
    v-=1
    if len(G[u])==0 and len(G[v])==0:
        G[u].append(v)
        G[v].append(u)
        ans.append(i+1)
print(len(ans))
for a in ans:
    print(a)