from ast import Store
from heapq import heappush,heappop
N = int(input())
q = []
ans = []
for i in range(1,2*N):
    heappush(q,(-i,i))
while q:
    S = []
    store = []
    n = N
    while n:
        t,s = heappop(q)
        t*=-1
        n-=1
        store.append((t,s))
        S.append(s)
    for t,s in store:
        if t == 1:
            pass
        else:
            heappush(q,(-(t-1),s))
    store = []
    ans.append(S)
    S = []
print(len(ans))
for s in ans:
    print(*s)