t = input()
if t == 'треугольник':
    a = int(input())
    b = int(input())
    c = int(input())
    p = (a + b + c)/2
    print (int(p *(p - a) * (p - b) * (p - c)) ** .5)
elif t == 'прямоугольник':
    a = int(input())
    b = int(input())
    print(a * b)
else:
    r = float(input())
    print(3.14 * (r * r))