1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
#include <bits/stdc++.h>
#define boost                                                                  \
  ios_base::sync_with_stdio(0);                                                \
  cin.tie(0);                                                                  \
  cout.tie(0)
#define ll long long
#define st first
#define nd second
using namespace std;

const int N(1e2 + 13);

int n, q, k;

vector<int> V[N];

int countBits(int k) {
  int bits = 0;
  while (k != 0) {
    bits++;
    k >>= 1;
  }
  return bits;
}

void initGraph() {
  for (int i = 1; i < n - 3; i += 3) {
    V[i].push_back(i + 1);
    V[i].push_back(i + 3);
    V[i + 1].push_back(i + 2);
    V[i + 1].push_back(i + 3);
  }
  V[n - 3].push_back(n);
}

void setGraph() {
  for (int i = 0; i < countBits(k) - 1; i++) {
    if ((1 << i) & k) {
      V[3 * (i + 1)].push_back(n);
    }
  }
}

void printGraph() {
  cout << n << endl;
  for (int i = 1; i <= n; i++) {
    if (V[i].size() > 0) {
      cout << V[i][0] << " ";
      if (V[i].size() > 1) {
        cout << V[i][1] << " ";
      } else {
        cout << "-1";
      }
    } else {
      cout << "-1 -1";
    }
    cout << endl;
  }
}

// int goThroughBits(int k) {
//   for (int i = 1; i <= countBits(k); i++) {
//   }
// }

int main() {
  boost;
  cin >> k;
  n = 3 * countBits(k) + 1;
  initGraph();
  setGraph();
  printGraph();
}