a            b            c
  x       1.809017     3.118034    12.871834
  f       0.334742    -0.297428     0.196191
             a            b            c
  x       2.309017     3.618034     4.520578
  f       0.050679    -0.393423    -0.315731
             a            b            c
  x       2.000000     2.809017     7.472735
  f       0.223891    -0.188717     0.269934
             a            b            c
  x       3.309017     4.271136     5.827878
  f      -0.346269    -0.365838     0.100316
             a            b            c
  x       3.000000     3.809017     3.871458
  f      -0.260052    -0.402656    -0.402442
             a            b            c
  x       3.000000     3.500000     4.309017
  f      -0.260052    -0.380128    -0.359448
             a            b            c
  x       3.500000     4.000000     4.809017
  f      -0.380128    -0.397150    -0.237726
             a            b            c
  x       4.500000     4.000000     3.190983
  f      -0.320543    -0.397150    -0.317815
             a            b            c
  x       4.500000     3.761258     3.690983
  f      -0.320543    -0.401754    -0.398728
             a            b            c
  x       5.000000     4.190983     2.873393
  f      -0.177597    -0.377793    -0.214198