By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms. Run this solution at repl.io here.
a, b = 1, 1
fib_sum = 0
while b < 4000000:
a, b = b, a + b
if b % 2 == 0:
fib_sum += b
print(fib_sum)