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PlayGround

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<html>
  <table rules="groups" border="2" frame="void">
    <colgroup span="2">
    <colgroup span="3" style="width:2em">
    <colgroup span="3">
    <colgroup span="3">
    <thead>
    <tr>
      <td colspan="2"></td>
      <th colspan="3"style="text-align:center">1</th>
      <th colspan="3">2</th>
      <th colspan="3">3</th>
    <tr>
      <td colspan="2"></td>
      <th>a</th>
      <th>b</th>
      <th>c</th>
      <th>a</th>
      <th>b</th>
      <th>c</th>
      <th>a</th>
      <th>b</th>
      <th>c</th>
    </tr>
    </thead>
    <tbody>
    <tr>
      <th rowspan="3">1</th>
      <th>a</th>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
    </tr>
    <tr>
      <th>b</th>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
    </tr>
    <tr>
      <th>c</th>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
      <td>0</td><td>1</td><td>2</td>
    </tr>
    </tbody>
  </table>
</html>