'''
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

	1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
'''


# f2 + f5 + f8 + ...
def sum_even_fibs():
	a = 1
	b = 2
	i = 0
	
	sum_fibs = 2
	while (a < 4000000) and (b < 4000000):
		f = a + b
		a = b
		b = f
		i = i + 1
		if ( i == 3):
			sum_fibs = sum_fibs + f
			i = 0

	print sum_fibs	
			

sum_even_fibs()

# soln: 4613732
