def dist(a, b):
  return ((a[0] - b[0])**2 + (a[1] - b[1])**2)**0.5

def f(poly):
  mxdist = 0
  for a in poly:
    for b in poly:
      mxdist = max(mxdist, dist(a, b))
  p = 0
  for i in range(len(poly)):
    j = (i + 1) % len(poly)
    p += dist(poly[i], poly[j])
  return mxdist / p