#include <iostream>
#include <vector>
#include <math.h>

using namespace std;

#define point pair<double, double>

#define deg_to_rad (3.1415926 / 180)

int main()
{
  // Where we are
  double x = 0.0;
  double y = 0.0;

  // Where we are facing
  double facing = 0.0;

  // The new readings
  double dist, angle;

  // Where we've been, now in cartesian
  vector<point> points;

  // Note where we started
  points.push_back(point(0.0, 0.0));

  // Read the info
  while (cin >> dist >> angle)
    {      
      // Move x and move y (the 12 is to convert inches to feet)
      x += dist * sin(facing * deg_to_rad) / 12;
      y += dist * cos(facing * deg_to_rad) / 12;

      // Break if we are done
      if (angle == 0) break;

      // Note where we are
      points.push_back(point(x, y));

      // And change the facing for next time
      facing += angle;

    }

  // now we count up the area: the area of n + 1 points is
  // 1 .. n: delta x * avg y (this overcounts in some cases, but
  // then subtracts off the overcount on the way back.  Very nice actually.)
  double area = 0.0;

  // Do the loop
  for (int i = 0; i < points.size() - 1; i++)
    {
      // Add the area of this trapezoid
      area += (points[i + 1].first  - points[i].first) * 
	(points[i + 1].second + points[i].second) / 2;
    }

  // Round and make sure the area is positive
  cout << abs(round(area)) << endl;
}