"""
    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.
"""

f1, f2 = 1, 2
fib_sum = 0
while f2 < 4000000:
    if f2 % 2 == 0:
        fib_sum += f2
    f1, f2 = f2, f1 + f2
print(fib_sum)
