gr=[[] for i in range(90)]
N=int(input())
for i in range(N):
	X,Y=map(int,input().split())
	x=X%10
	y=Y%9
	if (y//9)%2:
		x=(x+5)%10
	gr[x*9+y].append(i+1)
mx=[]
for i in gr:
	mx=max(mx,i,key=len)
print(len(mx))
print(*mx)