notes/school/di-ma/20181031_1-ex_ug.dot

graph g {
    {
        rank="same";
        1;
        2;
    }

    {
        rank="same";
        4;
        3 [ style="invisible" ];
    }

    1 -- 2;
    1 -- 3 [ style="invisible" ];
    1 -- 4;
    3 -- 2 [ style="invisible" ];
    2 -- 4;
    2 -- 5;
}