Figures

import math

# square, rectangle, circle или triangle):
shape = input()

if shape == "square":
    a = float(input())
    face = a * a
    print(round(face,3))
elif shape == "rectangle":
    a = float(input())
    b = float(input())
    face = a * b
    print(round(face,3))
elif shape == "circle":
    radius = float(input())
    face = math.pi * (radius * radius)
    print(round(face,3))
elif shape == "triangle":
    a = float(input())
    b = float(input())
    face = (a * b) / 2
    print(round(face,3))