#include<bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin >> n;
    if(n<=5)
        cout << -1 << endl;
    else
    {
        cout << "1 2\n1 3\n1 4\n2 5\n2 6\n";
        int i;
        for(i=7;i<=n;i++)
            cout << "1 "<< i << endl;
    }
    for(int i=2;i<=n;i++)
        cout << "1 "<< i << endl;
}