graph G {
    compound="true"
    rankdir="TB"
    bgcolor="white"
    fontname="Tahoma"

    node [
        fixedsize="false"
        fontname="Tahoma"
        color="white"
        fillcolor="grey"
        fontcolor="black"
        shape="box"
        style="filled"
        penwidth="1.0"
    ]
    edge [
        fontname="Arial"
        color="#00688b"
        fontcolor="black"
        fontsize="12"
        arrowsize="0.5"
        penwidth="1.0"
    ]




    "ustcwg@gmail.com" -- "zhjwpku@gmail.com" [label=" 30 ", penwidth="10", color="#00688bFF"];
    "guotao.yugt@gmail.com" -- "zhjwpku@gmail.com" [label=" 28 ", penwidth="9", color="#00688bED"];
    "ustcwg@gmail.com" -- "guotao.yugt@gmail.com" [label=" 16 ", penwidth="5", color="#00688bA5"];
    "ustcwg@gmail.com" -- "ying.cai.cn@gmail.com" [label=" 4 ", penwidth="1", color="#00688b5E"];
    "li.davidm96@gmail.com" -- "zhjwpku@gmail.com" [label=" 3 ", penwidth="1", color="#00688b5E"];
    "ying.cai.cn@gmail.com" -- "zhjwpku@gmail.com" [label=" 3 ", penwidth="1", color="#00688b5E"];
    "ying.cai.cn@gmail.com" -- "guotao.yugt@gmail.com" [label=" 3 ", penwidth="1", color="#00688b5E"];
    "li.davidm96@gmail.com" -- "guotao.yugt@gmail.com" [label=" 1 ", penwidth="1", color="#00688b4C"];

}