#include <bits/stdc++.h>

using namespace std;

const int M = 1 << 18 | 5;

int n;
pair<int, int> e[M];
int fa[M];

inline int Gfa(int i)
{
    return i == fa[i] ? i : fa[i] = Gfa(fa[i]);
}
inline bool Check(int l, int r)
{
    for(int i = 1; i <= n; i ++ ) fa[i] = i;
    for(int i = l; i <= r; i ++ )
    {
        if(Gfa(e[i].first) == Gfa(e[i].second)) return 0;
        fa[Gfa(e[i].first)] = Gfa(e[i].second);
    }
    return 1;
}
inline void SelfEval()
{
    for(int i = 1; i <= n * (n - 1) / 2; i ++ ) e[i + n * (n - 1) / 2] = e[i];
    for(int i = 1; i <= n * (n - 1) / 2; i ++ )
        if(!Check(i, i + n - 2))
        {
            printf("#%d\n", i);
            return ;
        }
}

int main()
{
    scanf("%d", &n);
    if(n & 1)
    {
        for(int i = 1; i <= n / 2; i ++ ) e[i] = make_pair(1, i + 1);
        reverse(e + 1, e + n / 2 + 1);
        for(int i = n / 2 + 1; i < n; i ++ ) e[i] = make_pair((n + 1) / 2, i + 1);
        reverse(e + n / 2 + 1, e + n);
        for(int i = n; i <= n * (n - 1) / 2; i ++ )
        {
            e[i] = e[i - n + 1];
            e[i].first  = e[i].first  == 1 ? n : e[i].first  - 1;
            e[i].second = e[i].second == 1 ? n : e[i].second - 1;
        }
    }
    else
    {
        for(int i = 1, j = 1; i < n; i ++ )
        {
            e[j ++ ].first = 1;
            for(int k = 1; k < n / 2; k ++ ) e[j ++ ].first = i + 1;
        }
        for(int i = 0, j = 1; i < n / 2; i ++ )
        {
            for(int k = 2; k != n + 1; k = k == n ? 3 : k + 2)
            {
                e[j ++ ].second = k;
            }
        }
    }
    for(int i = 1; i <= n * (n - 1) / 2; i ++ )
    {
        if(e[i].first > e[i].second) swap(e[i].first, e[i].second);
        printf("%d %d\n", e[i].first, e[i].second);
    }
    // SelfEval();
    return 0;
}