int main()
{
    unsigned int n,m;
    cin >> n; cin >> m;
    if (m > n)
       {
           return (0);
       }

    for (unsigned int index = (n/2 + n%2); index <= n; index++)
    {
        if(index%m ==0)
            {
                cout << index;
                break;
            }
    }

    return(0);
}