---

import math

def quadrilateral_area(points):
    center_x = sum(p[0] for p in points) / 4
    center_y = sum(p[1] for p in points) / 4
    
    def angle(p):
        return math.atan2(p[1] - center_y, p[0] - center_x)
    
    sorted_points = sorted(points, key=angle)
    
    x1, y1 = sorted_points[0]
    x2, y2 = sorted_points[1]
    x3, y3 = sorted_points[2]
    x4, y4 = sorted_points[3]
    
    area = abs((x1*y2 - x2*y1) + (x2*y3 - x3*y2) + 
               (x3*y4 - x4*y3) + (x4*y1 - x1*y4)) / 2
    
    return area

points = []
for i in range(4):
    coords = tuple(map(float, input().split(',')))
    points.append(coords)

result = quadrilateral_area(points)
print(result)