Problem: Leo Jr. draws pictures in his notebook with checkered sheets (that is, each sheet has a regular square grid printed on it). We can assume that the sheets are infinitely large in any direction.

To draw a picture, Leo Jr. colors some of the cells on a sheet gray. He considers the resulting picture beautiful if the following conditions are satisfied:

  * The picture is connected, that is, it is possible to get from any gray cell to any other by following a chain of gray cells, with each pair of adjacent cells in the path being neighbours (that is, sharing a side).
  * Each gray cell has an even number of gray neighbours.
  * There are exactly n gray cells with all gray neighbours. The number of other gray cells can be arbitrary (but reasonable, so that they can all be listed).



Leo Jr. is now struggling to draw a beautiful picture with a particular choice of n. Help him, and provide any example of a beautiful picture.

To output cell coordinates in your answer, assume that the sheet is provided with a Cartesian coordinate system such that one of the cells is chosen to be the origin (0, 0), axes 0x and 0y are orthogonal and parallel to grid lines, and a unit step along any axis in any direction takes you to a neighbouring cell.

Input

The only line contains a single integer n (1 ≤ n ≤ 500) — the number of gray cells with all gray neighbours in a beautiful picture.

Output

In the first line, print a single integer k — the number of gray cells in your picture. For technical reasons, k should not exceed 5 ⋅ 10^5.

Each of the following k lines should contain two integers — coordinates of a gray cell in your picture. All listed cells should be distinct, and the picture should satisdfy all the properties listed above. All coordinates should not exceed 10^9 by absolute value.

One can show that there exists an answer satisfying all requirements with a small enough k.

Example

Input


4


Output


12
1 0
2 0
0 1
1 1
2 1
3 1
0 2
1 2
2 2
3 2
1 3
2 3

Note

The answer for the sample is pictured below:

<image>

Solution (in PYTHON3):

Solution:
from sys import stdin
from collections import deque
# https://codeforces.com/contest/1354/status/D
mod = 10**9 + 7
import sys
import random
# sys.setrecursionlimit(10**6)
from queue import PriorityQueue
from collections import Counter as cc
# def rl():
#     return [int(w) for w in stdin.readline().split()]
from bisect import bisect_right
from bisect import bisect_left
from collections import defaultdict
from math import sqrt,factorial,gcd,log2,inf,ceil
# map(int,input().split())
# # l = list(map(int,input().split()))
# from itertools import permutations
import heapq
# input = lambda: sys.stdin.readline().rstrip()
input = lambda : sys.stdin.readline().rstrip()
from sys import stdin, stdout
from heapq import heapify, heappush, heappop
from itertools import permutations
from math import factorial as f

# def ncr(x, y):
#     return f(x) // (f(y) * f(x - y))
def ncr(n, r, p):
    num = den = 1
    for i in range(r):
        num = (num * (n - i)) % p
        den = (den * (i + 1)) % p
    return (num * pow(den,
                      p - 2, p)) % p

import sys

# input = sys.stdin.readline
# LCA
# def bfs(na):
#
#     queue = [na]
#     boo[na] = True
#     level[na] = 0
#
#     while queue!=[]:
#
#         z = queue.pop(0)
#
#         for i in hash[z]:
#
#             if not boo[i]:
#
#                 queue.append(i)
#                 level[i] = level[z] + 1
#                 boo[i] = True
#                 dp[i][0] = z
#
#
#
# def prec(n):
#
#     for i in range(1,20):
#
#         for j in range(1,n+1):
#             if dp[j][i-1]!=-1:
#                 dp[j][i] = dp[dp[j][i-1]][i-1]
#
#
# def lca(u,v):
#     if level[v] < level[u]:
#         u,v = v,u
#
#     diff = level[v] - level[u]
#
#
#     for i in range(20):
#         if ((diff>>i)&1):
#             v = dp[v][i]
#
#
#     if u == v:
#         return u
#
#
#     for i in range(19,-1,-1):
#         # print(i)
#         if dp[u][i] != dp[v][i]:
#
#             u = dp[u][i]
#             v = dp[v][i]
#
#
#     return dp[u][0]
#
# dp = []
#
#
# n = int(input())
#
# for i in range(n + 10):
#
#     ka = [-1]*(20)
#     dp.append(ka)


# class FenwickTree:
#     def __init__(self, x):
#         """transform list into BIT"""
#         self.bit = x
#         for i in range(len(x)):
#             j = i | (i + 1)
#             if j < len(x):
#                 x[j] += x[i]
#
#     def update(self, idx, x):
#         """updates bit[idx] += x"""
#         while idx < len(self.bit):
#             self.bit[idx] += x
#             idx |= idx + 1
#
#     def query(self, end):
#         """calc sum(bit[:end])"""
#         x = 0
#         while end:
#             x += self.bit[end - 1]
#             end &= end - 1
#         return x
#
#     def find_kth_smallest(self, k):
#         """Find largest idx such that sum(bit[:idx]) <= k"""
#         idx = -1
#         for d in reversed(range(len(self.bit).bit_length())):
#             right_idx = idx + (1 << d)
#             if right_idx < len(self.bit) and k >= self.bit[right_idx]:
#                 idx = right_idx
#                 k -= self.bit[idx]
#         return idx + 1



# import sys
# def rs(): return sys.stdin.readline().strip()
# def ri(): return int(sys.stdin.readline())
# def ria(): return list(map(int, sys.stdin.readline().split()))
# def prn(n): sys.stdout.write(str(n))
# def pia(a): sys.stdout.write(' '.join([str(s) for s in a]))
#
#
# import gc, os
#
# ii = 0
# _inp = b''
#
#
# def getchar():
#     global ii, _inp
#     if ii >= len(_inp):
#         _inp = os.read(0, 100000)
#         gc.collect()
#         ii = 0
#     if not _inp:
#         return b' '[0]
#     ii += 1
#     return _inp[ii - 1]
#
#
# def input():
#     c = getchar()
#     if c == b'-'[0]:
#         x = 0
#         sign = 1
#     else:
#         x = c - b'0'[0]
#         sign = 0
#     c = getchar()
#     while c >= b'0'[0]:
#         x = 10 * x + c - b'0'[0]
#         c = getchar()
#     if c == b'\r'[0]:
#         getchar()
#     return -x if sign else x

# fenwick Tree

# n,q = map(int,input().split())
#
#
# l1 = list(map(int,input().split()))
#
# l2 = list(map(int,input().split()))
#
# bit = [0]*(10**6 + 1)
#
# def update(i,add,bit):
#
#     while i>0 and i<len(bit):
#
#         bit[i]+=add
#         i = i + (i&(-i))
#
#
# def sum(i,bit):
#     ans = 0
#     while i>0:
#
#         ans+=bit[i]
#         i = i - (i & ( -i))
#
#
#     return ans
#
# def find_smallest(k,bit):
#
#     l = 0
#     h = len(bit)
#     while l<h:
#
#         mid = (l+h)//2
#         if k <= sum(mid,bit):
#             h = mid
#         else:
#             l = mid + 1
#
#
#     return l
#
#
# def insert(x,bit):
#     update(x,1,bit)
#
# def delete(x,bit):
#     update(x,-1,bit)
# fa = set()
#
# for i in l1:
#     insert(i,bit)
#
#
# for i in l2:
#     if i>0:
#         insert(i,bit)
#
#     else:
#         z = find_smallest(-i,bit)
#
#         delete(z,bit)
#
#
# # print(bit)
# if len(set(bit)) == 1:
#     print(0)
# else:
#     for i in range(1,n+1):
#         z = find_smallest(i,bit)
#         if z!=0:
#             print(z)
#             break
#

# service time problem


# def solve2(s,a,b,hash,z,cnt):
#     temp = cnt.copy()
#     x,y = hash[a],hash[b]
#     i = 0
#     j = len(s)-1
#
#     while z:
#
#         if s[j] - y>=x-s[i]:
#             if temp[s[j]]-1 == 0:
#                 j-=1
#             temp[s[j]]-=1
#             z-=1
#
#
#         else:
#             if temp[s[i]]-1 == 0:
#                 i+=1
#
#             temp[s[i]]-=1
#             z-=1
#
#     return s[i:j+1]
#
#
#
#
#
# def solve1(l,s,posn,z,hash):
#
#     ans = []
#     for i in l:
#         a,b = i
#         ka = solve2(s,a,b,posn,z,hash)
#         ans.append(ka)
#
#         return ans
#
# def consistent(input, window, min_entries, max_entries, tolerance):
#
#     l = input
#     n = len(l)
#     l.sort()
#     s = list(set(l))
#     s.sort()
#
#     if min_entries<=n<=max_entries:
#
#         if s[-1] - s[0]<window:
#             return True
#         hash = defaultdict(int)
#         posn = defaultdict(int)
#         for i in l:
#             hash[i]+=1
#
#         z = (tolerance*(n))//100
#         poss_window = set()
#
#
#         for i in range(len(s)):
#                 posn[i] = l[i]
#                 for j in range(i+1,len(s)):
#                     if s[j]-s[i] == window:
#                         poss_window.add((s[i],s[j]))
#
#         if poss_window!=set():
#             print(poss_window)
#             ans = solve1(poss_window,s,posn,z,hash)
#             print(ans)
#
#
#         else:
#             pass
#
#     else:
#         return False
#
#
#
#
# l = list(map(int,input().split()))
#
# min_ent,max_ent = map(int,input().split())
# w = int(input())
# tol = int(input())
# consistent(l, w, min_ent, max_ent, tol)

# t = int(input())
#
# for i in range(t):
#
#     n,x = map(int,input().split())
#
#     l = list(map(int,input().split()))
#
#     e,o = 0,0
#
#     for i in l:
#         if i%2 == 0:
#             e+=1
#         else:
#             o+=1
#
#     if e+o>=x and o!=0:
#         z = e+o - x
#         if z == 0:
#             if o%2 == 0:
#                 print('No')
#             else:
#                 print('Yes')
#             continue
#         if o%2 == 0:
#             o-=1
#             z-=1
#             if e>=z:
#                 print('Yes')
#             else:
#                 z-=e
#                 o-=z
#                 if o%2!=0:
#                     print('Yes')
#                 else:
#                     print('No')
#
#         else:
#
#             if e>=z:
#                 print('Yes')
#             else:
#                 z-=e
#                 o-=z
#                 if o%2!=0:
#                     print('Yes')
#                 else:
#                     print('No')
#     else:
#         print('No')
#
#
#
#
#
#
#
# def dfs(n):
#     boo[n] = True
#     dp2[n] = 1
#     for i in hash[n]:
#         if not boo[i]:
#
#             dfs(i)
#             dp2[n] += dp2[i]




































#
#
# n = int(input())
# x = 0
# l = list(map(int,input().split()))
# for i in range(n):
#
#      x = l[i]|x
#
# z = list(bin(x)[2:])
# ha = z.copy()
# k = z.count('1')
# ans = 0
# # print(z)
# cnt = 0
# for i in range(20):
#
#
#         maxi = 0
#         idx = -1
#
#         for j in range(n):
#             k = bin(l[j])[2:]
#             k = '0'*(len(z) -len(k)) + k
#             cnt = 0
#             for i in range(len(z)):
#                 if k[i] == z[i] == '1':
#                     cnt+=1
#
#             maxi = max(maxi,cnt)
#             if maxi == cnt:
#                 idx = j
#         if idx!=-1:
#
#             k = bin(l[idx])[2:]
#             k = '0'*(len(z) -len(k)) + k
#
#             for i in range(len(z)):
#                 if k[i] == z[i] == '1':
#                     z[i] = '0'
#             l[idx] = 0
#
#
# ans = 0
# for i in range(len(z)):
#     if z[i] == '0' and ha[i] == '1':
#         ans+=1
# flip = 0
# for i in range(ans):
#     flip+=2**i
#
#
#
# print(flip)

# def search(k,l,low):
#
#     high = len(l)-1
#     z = bisect_left(l,k,low,high)
#
#     return z
#
#
#
#
#
#
# n,x = map(int,input().split())
#
# l = list(map(int,input().split()))
#
# prefix = [0]
# ha = [0]
# for i in l:
#     prefix.append(i + prefix[-1])
#     ha.append((i*(i+1))//2 + ha[-1])
# fin = 0
# print(prefix)
# for i in range(n):
#     ans = 0
#     if l[i]<x:
#
#
#         if prefix[-1]-prefix[i]>=x:
#
#             z = search(x+prefix[i],prefix,i+1)
#             print(z)
#             z+=i+1
#             k1 = x-(prefix[z-1]-prefix[i])
#             ans+=ha[z-1]
#             ans+=(k1*(k1+1))//2
#
#
#         else:
#             z1 = x - (prefix[-1]-prefix[i])
#             z = search(z1,prefix,1)
#
#             k1 = x-prefix[z-1]
#             ans+=ha[z-1]
#             ans+=(k1*(k1+1))//2
#
#
#
#
#     elif l[i]>x:
#         z1 = ((l[i])*(l[i]+1))//2
#         z2 = ((l[i]-x)*(l[i]-x+1))//2
#         ans+=z1-z2
#     else:
#         ans+=(x*(x+1))//2





# t = int(input())
#
# for _ in range(t):
#
#     s = list(input())
#     ans = [s[0]]
#
#     for i in range(1,len(s)-1,2):
#         ans.append(s[i])
#
#     ans.append(s[-1])
#     print(''.join(ans))
#
#
#
# t = int(input())
#
# for _ in range(t):
#
#     n = int(input())
#     l = list(map(int,input().split()))
#     ans = 0
#     for i in range(n):
#         if l[i]%2!=i%2:
#             ans+=1
#
#     if ans%2 == 0:
#         print(ans//2)
#     else:
#        print(-1)


# t = int(input())
#
# for _ in range(t):
#
#     n,k = map(int,input().split())
#     s = input()
#
#
#     ans = 0
#     ba = []
#     for i in range(n):
#         if s[i] == '1':
#             ba.append(i)
#     if ba == []:
#         for i in range(0,n,k+1):
#             ans+=1
#
#         print(ans)
#         continue
#
#     i = s.index('1')
#     c = 0
#     for x in range(i-1,-1,-1):
#         if c == k:
#             c = 0
#             ans+=1
#         else:
#             c+=1
#
#
#     while i<len(s):
#         count = 0
#         dis = 0
#         while s[i] == '0':
#             dis+=1
#             if dis == k:
#                 dis = 0
#                 count+=1
#             if dis<k and s[i] == '1':
#                 count-=1
#                 break
#             i+=1
#             if i == n:
#                 break
#         i+=1
#
#     print(ans)
#
#
#
#



































































































n = int(input())
x = 10**9
y = 0
print(4*(n+1) - n)
for i in range(n+1):

     print(x,y)
     print(x-1,y)
     print(x,y+1)
     x-=1
     y+=1

print(x,y)