#include <vector>
#include <iostream>

using namespace std;
using vekt = vector<int>;

void fill_vector(vekt &v);
bool is_even(int a);
int sum_even(vekt &v);

int main()
{
    vekt v;
    fill_vector(v);
    int sum = sum_even(v);
    cout << sum;
    return 0;
}

bool is_even(int a)
{
    if (a % 2 == 0) return true;
    else return false;
}

void fill_vector(vekt &v)
{
    for (int i = 1; i < 1001; i++)
        v.push_back(i);
}

int sum_even(vekt &v)
{
    int sum = 0;
    for (int i = 0; i < v.size(); i++)
    {
        if (is_even(v[i])) sum += v[i];
    }
    return sum;
}