"""
Even Fibonacci numbers

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.
"""

from collections import defaultdict

def even_fib(limit):
    a, b = 1, 1
    d = defaultdict(int)
    sum = 0

    while(True):
        number = a + b

        if number >= limit:
            return sum

        if number % 2 == 0:
            sum += number

        # ghetto swap
        number = a
        a = b
        b = number + b


print(even_fib(4000000))