Euler2

//By considering the terms in the Fibonacci sequence whose values do not exceed four million,
//find the sum of the even - valued terms.
#include <iostream>
using namespace std;

int main()
{
    long unsigned int x = 1, y = 2, sum = 2, ctr = 0;
    for (long unsigned int fibonacci = 3; fibonacci < 4000000; fibonacci = x + y)
    {
        if (fibonacci % 2 == 0)
        sum += fibonacci;
        if (ctr % 2 == 0)
            x = fibonacci;
        else
            y = fibonacci;
        ctr++;
    }
    cout << sum <<endl;
    system("pause");
    return 0;
}