Euler #002 - Even Fibonacci numbers - Using Math

# fib series: 1, 1, 2, 3, 5, 8, 13, 21, 34 ...
# even fib  :       2,       8,         34 ...

ans = 0
val = 2
while val < 40_00000:
    ans += val
    val = round(val * phi ** 3)
print(ans)