#include <iostream>

using namespace std;


int main()
{
  int N;
  cin >> N;
  double x0, y0, x1, y1, x2, y2;
  cin >> x0 >> y0;
  x1 = x0;
  y1 = y0;
  double sum = 0.0;
  for (int i = 1; i < N; i++) {
	cin >> x2 >> y2;
	sum += (x2 - x1) * (y2 + y1);
	x1 = x2;
	y1 = y2;
  }	
  sum += (x0 - x1) * (y0 + y1);
  
  if (sum < 0.0) {
	cerr << "Points are not clockwise" << endl;
	return 1;
  }
  return 42;
}