area_figures

from math import pi

type_of_the_figure = (input())
result = 0

if type_of_the_figure == 'square':
    side = float(input())
    result = side * side
elif type_of_the_figure == 'rectangle':
    side_1 = float(input())
    side_2 = float(input())
    result = side_1 * side_2
elif type_of_the_figure == 'circle':
    radius = float(input())
    result = pi * (radius ** 2)
elif type_of_the_figure == 'triangle':
    side = float(input())
    height = float(input())
    result = side * height / 2
print(f'{result:.3f}')