def fibonacci():
    """a generator for Fibonacci numbers, goes to next number in series on each call"""
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

f = fibonacci()
#print (type(f))
#print (next(f))
sum=0
while True:
    n=next(f)
    if (n % 2)==0:
        sum=sum+n
    if n>4000000:
        print (sum)
        break