h = (b - a)/N
	k = 0.0
	x = a+h
	for i in range(N/2):
		k += 4*f(x, n)
		x += 2*h

	x = a + 2*h
	for i in range(N/2-1):
		k += 2*f(x+h, n)
		x += 2*h

	k += f(a, n)
	k += f(b, n)
	k = (k*h)/3

	return k