from math import pi
figure = input()

if figure == 'square':
    a = float(input())
    print(f'{a*a:.3f}')

elif figure == 'rectangle':
    a = float(input())
    b = float(input())
    print(f'{a*b:.3f}')

elif figure == 'circle':
    r = float(input())
    print(f'{pi * (r ** 2):.3f}')

elif figure == 'triangle':
    a = float(input())
    h = float(input())
    print(f'{(a/2) * h:.3f}')