def tofixed(numObj, digits=0):
    return f"{numObj:.{digits}f}"


n = int(input())
ma = -8800555252512343
mi = 22813372281337322
mab = -880055525251234
k = 0
for i in range(n):
    a, b = map(int, input().split())
    if b == 0:
        k += 1
        if a > ma:
            ma = a
        if a < mi:
            mi = a
    else:
        if abs(b) > mab:
            mab = abs(b)
if mab == -880055525251234 or k < 2:
    print(tofixed(0, 6))
else:
    print(tofixed((abs(mi - ma) * mab / 2), 6))