+     +-----+-----+-----+-----+-----+     +
            "     "     |     "           |
            "  3  "  1  |  6  "           |
            "     "     |     "           |
+=====+=====+-----+=====+-----+=====+=====+
|     |     |     "     "     |     |     |
|  1  |  7  |  5  "     "  4  |  2  |  3  |
|     |     |     "     "     |     |     |
+-----+-----+-----+=====+-----+-----+=====+
|     |     |     |     "     |     "     |
|  6  |  4  |  8  |  2  "  5  |  8  "  8  |
|     |     |     |     "     |     "     |
+=====+=====+=====+=====+-----+=====+-----+
|     |     |     "     "     "     |     |
|  3  |  8  |  4  "     "  7  "  4  |  2  |
|     |     |     "     "     "     |     |
+-----+-----+=====+     +=====+-----+-----+
|     |     "     "     "     |     |     |
|  2  |  7  "  6  "     "  1  |  5  |  7  |
|     |     "     "     "     |     |     |
+-----+-----+-----+=====+=====+-----+-----+
|     |     "     |     |     "     |     |
|  6  |  1  "  8  |  2  |  1  "  6  |  3  |
|     |     "     |     |     "     |     |
+=====+-----+-----+-----+-----+=====+=====+
      "     "     |     |     |     "     |
      "  5  "  3  |  4  |  7  |  5  "     |
      "     "     |     |     |     "     |
+-----+-----+-----+-----+-----+-----+-----+