In [4]:
def find_radius(length):
    return length / 3.14159

In [5]:
def find_max_area(radius):
    return (3.14159*pow(radius, 2))/2

In [6]:
while True:
    length = int(raw_input())
    
    if length == 0:
        break
    
    radius = find_radius(length)
    print '%.2f' % find_max_area(radius)


1
0.16
0

In [ ]: