Untitled

// write your code

from math import pi
figures = input()

area = ''

if figures == "square":
    a = float(input())
    area = a * a
elif figures == 'rectangle':
    a = float(input())
    b = float(input())
    area = a * b
elif figures == "circle":
    r = float(input())
    area = r ** 2 * pi
elif figures == "triangle":
    a = float(input())
    h = float(input())
    area = a * h / 2

print(f"{area:.3f}")