#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int n;
int Nxt(int i) { return i % n + 1; }
int Pre(int i) { return (i - 2 + n) % n + 1; }
int main() {
	scanf("%d", &n);
	if (n & 1) {
		for (int i = 1; i <= n; i++) {
			for (int a = i, b = Nxt(i); a != b; a = Pre(a), b = Nxt(b)) {
				printf("%d %d\n", min(a, b), max(a, b));
			}
		}
	}
	else {
		n--;
		for (int i = 1; i <= n; i++) {
			for (int a = i, b = Nxt(i); a != b; a = Pre(a), b = Nxt(b)) {
				printf("%d %d\n", min(a, b), max(a, b));
			}
			printf("%d %d\n", i, n + 1);
		}
	}
	return 0;
}