#include <cstdlib>
#include <iostream>
#include <vector>

int main(int argc, char *argv[])
{
	int n= atoi(argv[1]);
	std::cout << "0\t1\n";
	for (int k=1; k<n-1; ++k)
		std::cout << k-1 << '\t' << k+1 << std::endl;
	std::cout << n-2 << '\t' << n-1 << "\t*\n\n";
	return EXIT_SUCCESS;
}