from math import dist
def solve(input):
    points = []
    for line in open(input):
        x,y = map(int, line.strip().split(","))
        points.append((x,y))

    def areas():
        for p in points:
            for q in points:
                if p != q:
                    yield area(p,q)

    print(max(areas()))

def area(p,q):
    dx = abs(p[0] - q[0]) + 1
    dy = abs(p[1] - q[1]) + 1
    return dx*dy

solve("sample")
solve("input")