#include <bits/stdc++.h>

using namespace std;

const int M = 1 << 18 | 5;

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

int main()
{
    scanf("%d", &n);
    int c = 0;
    if(n & 1)
    {
        for(int i = 1; i <= n / 2; i ++ ) e[ ++ c] = make_pair(i + 0, n + 1 - i);
        for(int i = 1; i <= n / 2; i ++ ) e[ ++ c] = make_pair(i + 1, n + 1 - i);
    }
    else
    {
        for(int i = 1; i <  n / 2; i ++ ) e[ ++ c] = make_pair(i, n + 0 - i);
        for(int i = 1; i <= n / 2; i ++ ) e[ ++ c] = make_pair(i, n + 1 - i);
    }
    for(int i = n; i <= n * (n - 1) / 2; i ++ )
    {
        e[i] = e[i - n + 1];
        if(e[i].first  <= n) e[i].first  = e[i].first  % n + 1;
        if(e[i].second <= n) e[i].second = e[i].second % n + 1;
    }
    for(int i = 1; i <= n * (n - 1) / 2; i ++ ) printf("%d %d\n", e[i].first, e[i].second);
    return 0;
}