now_lb = 1
now_ub = 2
cnt = 2
a = []
b = []

mx = 14

a.append(1)
b.append(2)
a.append(1)
b.append(3)
a.append(1)
b.append(4)
a.append(2)
b.append(5)
a.append(3)
b.append(6)
a.append(4)
b.append(7)
now_lb = 5
now_ub = 8
cnt = 8

for num in range(mx):
	old_cnt = cnt
	for i in range(now_lb, now_ub):
		a.append(i)
		b.append(cnt)
		cnt += 1
		a.append(i)
		b.append(cnt)
		cnt += 1
	if num == mx-1: break
	now_lb = cnt
	t_cnt = cnt
	for i in range(old_cnt, t_cnt):
		a.append(i)
		b.append(cnt)
		cnt += 1
	now_ub = cnt

a.append(cnt - 1)
b.append(cnt)

print(len(a) + 1)
for i, j in zip(a, b):
	print(i, j)