import sys

int1 = lambda x: int(x) - 1

# input = lambda: sys.stdin.buffer.readline()
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
i1 = lambda: int1(input())
mi = lambda: map(int, input().split())
mi1 = lambda: map(int1, input().split())
li = lambda: list(mi())
li1 = lambda: list(mi1())
lli = lambda n: [li() for _ in range(n)]

INF = float("inf")
mod = int(1e9 + 7)
# mod = 998244353

n = ii()
print(2 * n - 1)
c = [i for i in range(2 * n)]
cur = []
for i in range(1, 2 * n):
    while c[i] > 0:
        cur.append(i)
        if len(cur) == n:
            print(*cur)
            cur = []
        c[i] -= 1