Problem: Write a program that reads the coordinates of the vertices of a convex n-sided polygon (a polygon whose internal angles are less than 180 degrees, that is, a polygon that is not dented) and outputs its area. The vertices are named Vertex 1, Vertex 2, Vertex 3, ... Vertex n according to the order of edge connections.

However, n is 3 or more and 20 or less. You can also use the following formula to find the area S from the lengths a, b, and c of the three sides of the triangle.

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input

The input is given in the following format:


x1, y1
x2, y2
::
xn, yn


xi and yi are real numbers that represent the x and y coordinates of vertex i, respectively.

output

Outputs the area S (real number) on one line. The output can contain an error of 0.000001 or less.

Example

Input

0.0,0.0
0.0,1.0
1.0,1.0
2.0,0.0
1.0,-1.0


Output

2.500000

Solution (in PYTHON3):

Solution:
number = []
answer = 0
while 1:
    try:
        x, y = map(float, input().split(","))
        number.append((x, y))
    except:
        number.append(number[0])
        for i in range(len(number)-1):
            answer += (number[i][0] - number[i + 1][0]) * (number[i][1] + number[i+1][1])
        if answer < 0:
            answer = answer * (-1)
        print("{:.6f}".format(answer / 2))
        break