{ 1*x2 + 1*x3 = k56,
  1*x4 + 1*x16 = k57,
  1*x5 + 1*x15 = k58,
  1*x6 + 1*x17 = k59,
  1*x7 + 1*x8 = k60,
  1*x10 + 1*x11 = k61,
  1*x12 + 1*x13 = k62,
  1*x20 + 1*x21 = k63 }