#include <bits/stdc++.h>
using namespace std;
 
struct point
{
	double x, y;
};
 
bool corner(point a, point b, point c)
{
	return ((double)(c.x - b.x) * (a.y - b.y) - (double)(a.x - b.x) * (c.y - b.y)) > 0;
}
 
int main()
{
	int n;
	cin >> n;
	vector <point> p(n);
	vector <pair<point, point> > ans;
	for (int i = 0; i < n; i++)
	{
	    double a, b;
		cin >> a >> b;
		p[i] = {a, b};
	}
	p.push_back(p[0]);
	p.push_back(p[1]);
	for (int i = 0; i < p.size() - 2; i++)
		ans.push_back({p[i], p[i + 1]});
	//1 2 3 1 2
	for (int i = 1; i < p.size() - 1; i++)
	{
		if (!corner(p[i - 1], p[i], p[i + 1]))
		    cout << p[i - 1].x << " " << p[i - 1].y << "     " << p[i + 1].x << " " << p[i + 1].y << "\n";
	}
}

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