#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int first = 0, f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar()) {
    if (ch == '-') f = -1;
  }
  for (; isdigit(ch); ch = getchar()) {
    first = first * 10 + ch - 48;
  }
  return first * f;
}
const int mxN = 500;
int n;
int main() {
  n = read();
  printf("%d\n", 3 * n + 4);
  printf("%d %d\n", 0, 0);
  for (int i = 1; i <= n + 1; i++) {
    printf("%d %d\n", i - 1, i);
    printf("%d %d\n", i, i - 1);
    printf("%d %d\n", i, i);
  }
  return 0;
}
