#include <cstdio>
#include <algorithm>
#include<vector>
#include<queue>
#include<list>
#include<stack>

using namespace std;

int y,nod,minim,i,aux,n,k,x2,x1,j,p,s,unu,t,m,doi,x,st,dr,maxi,sol,maxi2,ok;
list <int> a[2000];
stack <int>stiva;

vector<int> circuit;


 void sterge(int nod, int vecin) {
     //sterg muchia dintre nod si vecinul sau
    a[nod].pop_front();
    list<int>::iterator it;
    for (it = a[vecin].begin(); it != a[vecin].end(); ++it)
        if (*it == nod) {
            a[nod].erase(it);
            break;
        }
}

 void euler(int nod) {
    int vecin;
    while(! a[nod].empty())
    {
        //printf("%d ",nod);
        vecin=a[nod].front();
        stiva.push(nod);
        sterge(nod,vecin);
        nod=vecin;
    }
}

void solve() {
    int nod = 1;
    do {
        euler(nod);
       // printf("\n");
        nod = stiva.top();
        stiva.pop();
        circuit.push_back(nod);
    }while (!stiva.empty());
}
void write()
{
    for(i=1;i<circuit.size();i++)
    {
        printf("%d %d\n",circuit[i-1],circuit[i]);
    }
    printf("1 %d",n);
}

int main()
{
    freopen ("domino2.in","r",stdin);
    freopen ("domino2.out","w",stdout);
    scanf("%d",&n);
    if(n%2==0)
    {
        printf("-1");
    }
    else {
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++){
        a[i].push_back(j);
        }
    }
    solve();
    write();

    }
}