#include<bits/stdc++.h>
using namespace std;
int n, vis[505][505], tot, cnte, fa[505];
pair<int, int> pr[250005];
int Get(int x) {
	return x == fa[x] ? x : fa[x] = Get(fa[x]);
}
int main() {
	srand(unsigned(time(NULL)));
	scanf("%d", &n);
	for(int i = 1; i <= n; ++ i)
		for(int j = i + 1; j <= n; ++ j)
			pr[++ cnte] = {i, j};
	int f = 0, c = 0;
	while(!f) {
		f = 1;
		++ c;
		random_shuffle(pr + 1, pr + cnte + 1);
		for(int i = 1; i <= cnte; ++ i) {
			for(int j = 1; j <= n; ++ j)
				fa[j] = j;
			for(int j = 1; j < n; ++ j) {
				int w = i + j - 1;
				if(w > cnte)
					w -= cnte;
				int u = Get(pr[w].first), v = Get(pr[w].second);
				if(fa[u] != fa[v]) {
					fa[u] = v;
					continue;
				}
				f = 0;
				break;
			}
			if(!f)
				break;
		}
	}
	for(int i = 1; i <= cnte; ++ i)
		printf("%d %d\n", pr[i].first, pr[i].second);
}