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
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#ifdef LOCAL
#define debug(...) __VA_ARGS__
#else
#define debug(...) {}
#endif

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie();
    cout.tie();
    int i = 0;
    int k;
    cin>>k;
    while ((1<<i) <= k) i++;
    int n = 2*i;
    cout<<n<<"\n";
    int pointer = 0;
    for (i = 1; i < n-1; i++){
        if (i%2){
            cout<<i+1<<" "<<i+2<<"\n";
            continue;
        }
        cout<<i+1<<" ";
        if ((1<<pointer)&k) cout<<n<<"\n";
        else cout<<-1<<"\n";
        pointer++;
    }
    cout<<-1<<" ";
    if ((1<<pointer)&k) cout<<n<<"\n";
    else cout<<-1<<"\n";
    cout<<-1<<" "<<-1<<"\n";
    return 0;
}