n = int(input())
count = [0]*90
l = [[] for i in range(90)]

for i in range(n):
    a,b = map(int,input().split())
    x = a%9
    y = b%10
    if a%18 >= 9:
        y = (y+5)%10
    count[x*10+y] += 1
    l[x*10+y].append(i+1)

print(max(count))
ind = count.index(max(count))
for i in l[ind]:
    print(i)