digraph g {
    node [ shape="circle" ];
    {
        rank="same";
        1;
        2;
    }

    {
        rank="same";
        4;
        3;
    }

    1 -> 2;
    2 -> 3;
    3 -> 1;
    4 -> 1;

    edge [ style="dotted" ];
    1 -> 3;
    2 -> 1;
    3 -> 2;
    4 -> 2;
    4 -> 3;
}