Project Euler Problem 2

問題

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, ...

Find the sum of all the even-valued terms in the sequence which do not exceed
four million.

ソース

sum = 0
x = 1
y = 2
while x <= 4000000 do
	x, y = y, x + y
	sum += x if x % 2 == 0
end
p sum

解答

4613732

感想

なぜ2が入らないのかが未だに謎。。。