file = open('19A.txt')
n = int(file.readline())
x = []
y = []
for i in range(n):
    x_0, y_0 = map(int, file.readline().split())
    if y_0 == 0:
        x += [x_0]
    else:
        y += [abs(y_0)]
x.sort()
y.sort()
print(0.5 * y[-1] * (x[-1] - x[0]))