a = [0, 1, 2]
dic = {(2, 1): 1}
maxx = 100

from sys import argv
if len(argv) > 0:
  maxx = int(argv[1])

def get(x, y):
  if y >= x:
    return a[x]
  return dic.get((x, y))

for n in xrange(3, maxx + 1):
  tmp = 0
  for i in xrange(1, n):
    tmp += get(n - i, i)
    dic.update({(n, i): tmp})
  a.append(tmp + 1)

print a[-1] - 1