#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int main(){
	int n;
	cin>>n;

	vector<P> ans;
	vector<int> deg(n);
	rep(i, n){
		int m=i-deg[i];
		if(i+m>=n) break;
		rep(j, m){
			ans.push_back(P(i, i+1+j));
			deg[i+1+j]++;
		}
	}

	for(P p : ans) cout<<(p.first+1)<<" "<<(p.second+1)<<endl;
	return 0;
}