rand5->rand7,rand7->rand10

int Random5()
{
    return rand() % 5 + 1;
}
int Random7()
{
    return rand() % 7 + 1;
}
int rand7()
{
    int i;
    do
    {
        i = 5 * (Random5() - 1) + Random5();
    } while (i > 21);
    return i % 7 + 1;
}
int rand10()
{
    int i;
    do
    {
        i = 7 * (Random7() - 1) + Random7();
    } while (i > 40);
    return i % 10 + 1;
}