#include <stdio.h>
#include <stdlib.h>

#define MAXN (100*1024)

struct point
{
  int x, y;
};

struct point list[MAXN];
int N, n;
int srt[MAXN], hull[MAXN];

int pcmp( const void *ptr1, const void *ptr2)
{
  int id1 = *(int *) ptr1;
  int id2 = *(int *) ptr2;
  int d = list[id1].y * list[id2].x - list[id1].x * list[id2].y;
  if( d != 0 ) return d;
  return list[id2].x * list[id2].x + list[id2].y * list[id2].y -
         list[id1].x * list[id1].x - list[id1].y * list[id1].y;
}

void swap( int id )
{
  int tmp = srt[0];
  srt[0] = id;
  srt[id] = tmp;
}

int solution( void )
{
  int i, sum = 0;

  n = 0;
  hull[n++] = srt[0];
  hull[n++] = srt[1];
  hull[n++] = srt[2];
  for( i = 3; i < N; ++i)
  {
    for( ; n > 2; --n)
    {
      struct point *p1 = &list[hull[n-2]], *p2 = &list[hull[n-1]], *p3 = &list[srt[i]];
      if( (p3->x - p1->x) * (p2->y - p1->y) - (p2->x - p1->x) * (p3->y - p1->y) < 0 ) break;
    }
    hull[n++] = srt[i];
  }

  if( n <= 2 ) return 0;
  hull[n] = srt[0];
  for( i = 0; i < n; ++i)
  {
    struct point *p1 = &list[hull[i]], *p2 = &list[hull[i+1]];
    sum += p1->x * p2->y - p1->y * p2->x;
  }
  if( sum < 0 ) sum = -sum;
  return sum;
}

int main( void )
{
  while( scanf( "%d", &N) == 1 )
  {
    int i, id = -1, res, x, y;
    for( i = 0; i < N; ++i)
    {
      scanf( "%d %d", &list[i].x, &list[i].y);
      if( id < 0 || list[id].y > list[i].y ||
          (list[id].y == list[i].y && list[id].x > list[i].x) ) id = i;
      srt[i] = i;
    }
    x = list[id].x, y = list[id].y;
    for( i = 0; i < N; ++i) list[i].x -= x, list[i].y -= y;
    swap( id );
    qsort( srt+1, N-1, sizeof(int), pcmp);
    res = solution();
    printf( "%d.%d0\n", res / 2, (res & 1) ? 5 : 0);
  }
  return 0;
}