import sys
import math
import time


def dotproduct(v1, v2):
    return sum((a * b) for a, b in zip(v1, v2))


def length(v):
    return math.sqrt(dotproduct(v, v))


def angle(l1, l2):
    if length(l1) * length(l2) == 0:
        return 0
    else:
        return math.acos(dotproduct(l1, l2) / (length(l1) * length(l2)))


def lines(v1, v2):
    return (v1[0] - v2[0], v1[1] - v2[1])


def find_min(listt, place):
    pointer = 0
    val = listt[pointer][0]
    for i in range(len(listt)):
        if val > listt[i][place]:
            val = listt[i][place]
            pointer = i
    return pointer


def find_max_angle(points, last_point, last_two_point):
    new_tracker = 0
    temp = 0
    for i in range(len(points)):
        result = angle(lines(points[i], last_point), lines(last_two_point, last_point))
        if result > temp:
            temp = result
            new_tracker = i
    return points[new_tracker], new_tracker


def area(contour):
    results = 0
    for i in range(1, len(contour) - 1):
        sin_angle = angle(lines(contour[0], contour[i]), lines(contour[i + 1], contour[i]))
        results += math.sin(sin_angle) * length(lines(contour[0], contour[i])) * length(
            lines(contour[i + 1], contour[i])) * 0.5
    return results


while True:
    num = int(input())
    if num == 0:
        break
    points = []
    for i in range(num):
        points += list(map(int, input().split())),
    pointer = find_min(points, 0)

    tracker1 = 0
    tracker2 = 0
    temp = 0
    for i in range(len(points)):
        for j in range(i + 1, len(points)):
            angle_result = angle(lines(points[i], points[pointer]), lines(points[j], points[pointer]))
            if angle_result > temp:
                temp = angle_result
                tracker1 = i
                tracker2 = j
    contour = [points[tracker1], points[pointer], points[tracker2]]
    del points[tracker2], points[pointer]

    while True:
        new_point, new_tracker = find_max_angle(points, contour[-1], contour[-2])
        if new_point == contour[0]:
            print("{:.1f}".format(area(contour)))
            break
        else:
            contour.append(new_point)
            del points[new_tracker]
