#include <bits/stdc++.h>
using namespace std;
pair<int, int> afis[1503];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int n, cnt = 0, i, x = 1;
  cin >> n;
  afis[++cnt] = {0, 0};
  while (x <= n + 1) {
    afis[++cnt] = {x, x};
    afis[++cnt] = {x, x - 1};
    afis[++cnt] = {x - 1, x};
    x++;
  }
  cout << cnt << '\n';
  for (i = 1; i <= cnt; i++)
    cout << afis[i].first << " " << afis[i].second << '\n';
  return 0;
}
