import sys
input = sys.stdin.readline

N,M=map(int,input().split())

EDGE=[list(map(int,input().split())) for i in range(M)]

USE=[0]*(N+1)
ANS=[]
for i in range(M):
    x,y = EDGE[i]
    if USE[x]==0 and USE[y]==0:
        USE[x]=1
        USE[y]=1
        ANS.append(i+1)

print(len(ANS))
for ans in ANS:
    print(ans)