duplicarea cifrelor pare a unui numar

#include<iostream>
using namespace std;
void citire(unsigned &n)
{
    do
    {
        cout << "n="; cin >> n;
    } while (n < 1 || n>10000);
}
void duplicare(unsigned n, int &d)
{
    d = 0;
    int cifre[5] = { 0 };
    int i = 4;
    while (n != 0)
    {
        cifre[i] = n % 10;
        i--;
        n /= 10;
    }
    bool par = false;
    for (int k = i + 1; k <= 4; k++)
        if (cifre[k] % 2 == 0)
        {
            par = true;
            d = d * 10 + cifre[k];
            d = d * 10 + cifre[k];
        }
        else
            d = d * 10 + cifre[k];
    if (!par)
        d = -1;

}
int main()
{
    unsigned n;
    int d;
    citire(n);
    duplicare(n, d);
    cout << "d=" << d;
    cout << endl << endl;
    system("pause");
    return 0;
}