s = str(raw_input('figure '))

if s == 'rect':
  a = int(input('a '))
  b = int(input('b '))
  print(a * b)

elif s == 'circ':
  r = int(input('r '))
  print(3.14 * r **2)

elif s == 'triang':
  a = int(input('a '))
  b = int(input('b '))
  c = int(input('c '))
  p = (a + b +c)/2.0
  print((p*(p - a)*(p - b)*(p - c))**0.5)