N,M=map(int,input().split())
use=[False]*(N+1)
ans=[]
for i in range(M):
    u,v=map(int,input().split())
    if (not use[u]) and (not use[v]):
        use[u]=True
        use[v]=True
        ans.append(i+1)
print(len(ans))
print(*ans,sep='\n')