/* Check cf5-opt.vim defs.
VIM: let g:lcppflags="-std=c++11 -O2 -pthread"
VIM: let g:wcppflags="/O2 /EHsc /DWIN32"
*/
#include <iostream>

/*
Even Fibonacci numbers
Problem 2
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.

Solution:
4613732
*/

int main ( void )
{

	int x = 1;
	int y = 2;
	int z = x+y;
	int s = 0;
	while ( z < 4000000 )
	{
		s+= z;
		x = y;
		y = z;
		z = x+y;
	}
	if ( y%2 )
	{
		s -= y;
		if ( x%2 )
			s -= x;
	}
	s /= 2;
	s += 2;
	std::cout << s << std::endl;

	return 0;
}