#!/usr/bin/env python
"""
Created on 14 Mar 2017

@author: David Doblas Jiménez
@email: daviddoji@pm.me

Solution for problem 2 of Project Euler
https://projecteuler.net/problem=2
"""

from utils import timeit


@timeit("Problem 2")
def compute():
    """
    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, ...

    Find the sum of all the even-valued terms in the sequence which do not
    exceed four million.
    """

    ans = 0
    limit = 4_000_000
    x, y = 1, 1
    z = x + y  # Because every third Fibonacci number is even
    while z <= limit:
        ans += z
        x = y + z
        y = z + x
        z = x + y

    return ans


if __name__ == "__main__":
    print(f"Result for problem 2 is {compute()}")