notes/school/di-ma/20181031_1-c4.dot

graph c4 {
    node [ shape="point" ];

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

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

    1 -- 2;
    3 -- 4;
    1 -- 3;
    2 -- 4;
}