from math import log

def B(x):
  return -10*x**2 + 10*x + 20*x*log(x)

def rech_benef(pas):
  prod = []
  a = 1
  b = a+pas
  while a < 3:
    if (B(a) <= 8 <= B(b)):
      prod.append(a)
    else if (B(a) >= 8 >= B(b)):
      prod.append(a)
    a = b
    b = a+pas
  return prod