#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  printf("%d\n", 4 + 3 * n);
  printf("0 0\n0 1\n1 0\n1 1\n");
  for (int i = 1; i <= n; i++) {
    printf("%d %d\n%d %d\n%d %d\n", i, i + 1, i + 1, i, i + 1, i + 1);
  }
  return 0;
}
