def test_fib(n):
   a, b = 0.0, 1.0
   for i in range(n):
      a, b = a + b, a
   print (a)

def integrate_f(a, b, N):
    s = 0
    dx = (b - a) / N
    for i in range(N):
        s += (a + i * dx) ** 2 - (a + i * dx)
    return s * dx