#include <string>
#include <vector>
#include <fstream>
using namespace std;

#include <stdio.h>
#include <math.h>


struct point
{
	double x;
	double y;
};

int main()
{
	ifstream input("diplomatic.in");
	int count = 0;
	while (input.good())
	{
		int n;
		input >> n;
		if (input.eof()) break;
		
		vector<point> loc(n+1);
		
		for (int i = 0; i < n; i++)
		{
			input >> loc[i].x >> loc[i].y;		
		}
		loc[n] = loc[0];
		
		if (count++) printf("\n");
		
		printf("%d ", n);
		for (int i = 0; i < n; i++)
		{
			point neu;		
			neu.x = (loc[i+1].x - loc[i].x) / 2;
			neu.y = (loc[i+1].y - loc[i].y) / 2; 			
			neu.x += loc[i].x;
			neu.y += loc[i].y;
		
//			neu.x = floor(neu.x + 0.5);
//			neu.y = floor(neu.y + 0.5);
			
//			cout << neu.x << " " << neu.y;
//			if (i != n) cout << " ";

			printf("%.0f %.0f", neu.x, neu.y); 
			if (i != n-1) printf(" ");
		
		}
		
		
	
	}
}