#!/usr/bin/env python3

# 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 projecteuler import timing


@timing
def p002() -> None:
    N = 4000000

    fib1 = 1
    fib2 = 2
    fibn = fib1 + fib2
    _sum = 2

    # Simple brute-force approach: generate every value in the Fibonacci
    # sequence smaller than 4 million and if it's even add it to the total.
    while fibn < N:
        if fibn % 2 == 0:
            _sum = _sum + fibn

        fib1 = fib2
        fib2 = fibn
        fibn = fib1 + fib2

    print('Project Euler, Problem 2')
    print(f'Answer: {_sum}')


if __name__ == '__main__':
    p002()