2_sum_even_fibonacci.py

"""

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.

"""


x,y  = 1, 1

even_fib_sum = 0

limit = 4000000

while y <= limit:

    even_fib_sum += y if y % 2 == 0 else 0

    x, y = y, x + y

print(even_fib_sum)