{ diff(x1, t) = 0,
  diff(x2, t) = (1*(k1*x15 - k2*x2) + 1*k18*k4*x3*k20)/k18,
  diff(x3, t) = (1*(k1*x16 - k2*x3) + (-1)*k18*(k6*x3*x8 - k7*x7) + (-2)*k18*(k6*x3*x3 - k7*x6) + (-1)*k18*k4*x3*k20 + (-1)*k18*(k6*x3*x5 - k7*x9))/k18,
  diff(x4, t) = (1*k18*k4*x5*k20 + 1*(k1*x17 - k2*x4))/k18,
  diff(x5, t) = ((-1)*k18*k4*x5*k20 + 1*(k1*x18 - k2*x5) + (-2)*k18*(k6*x5*x5 - k7*x11) + (-1)*k18*(k6*x3*x5 - k7*x9) + (-1)*k18*(k6*x5*x8 - k7*x10))/k18,
  diff(x6, t) = (1*k5*x12 + 1*k18*(k6*x3*x3 - k7*x6))/k18,
  diff(x7, t) = (1*k18*(k6*x3*x8 - k7*x7) + 1*k5*x13)/k18,
  diff(x8, t) = (1*(k1*x14 - k1*x8) + (-1)*k18*(k6*x3*x8 - k7*x7) + (-1)*k18*(k6*x5*x8 - k7*x10))/k18,
  diff(x9, t) = (1*k18*(k6*x3*x5 - k7*x9) + 1*k5*x19)/k18,
  diff(x10, t) = (1*k18*(k6*x5*x8 - k7*x10) + 1*k5*x20)/k18,
  diff(x11, t) = (1*k18*(k6*x5*x5 - k7*x11) + 1*k5*x21)/k18,
  diff(x12, t) = ((-1)*k5*x12 + 1*k19*(k6*x16*x16 - k7*x12))/k19,
  diff(x13, t) = (1*k19*(k6*x16*x14 - k7*x13) + (-1)*k5*x13)/k19,
  diff(x14, t) = ((-1)*(k1*x14 - k1*x8) + (-1)*k19*(k6*x16*x14 - k7*x13) + (-1)*k19*(k6*x18*x14 - k7*x20))/k19,
  diff(x15, t) = ((-1)*(k1*x15 - k2*x2) + (-1)*k19*k3*x23*x15)/k19,
  diff(x16, t) = ((-1)*(k1*x16 - k2*x3) + 1*k19*k3*x23*x15 + (-1)*k19*(k6*x16*x14 - k7*x13) + (-2)*k19*(k6*x16*x16 - k7*x12) + (-1)*k19*(k6*x16*x18 - k7*x19))/k19,
  diff(x17, t) = ((-1)*k19*k3*x17*x23 + (-1)*(k1*x17 - k2*x4))/k19,
  diff(x18, t) = (1*k19*k3*x17*x23 + (-1)*(k1*x18 - k2*x5) + (-2)*k19*(k6*x18*x18 - k7*x21) + (-1)*k19*(k6*x16*x18 - k7*x19) + (-1)*k19*(k6*x18*x14 - k7*x20))/k19,
  diff(x19, t) = (1*k19*(k6*x16*x18 - k7*x19) + (-1)*k5*x19)/k19,
  diff(x20, t) = (1*k19*(k6*x18*x14 - k7*x20) + (-1)*k5*x20)/k19,
  diff(x21, t) = (1*k19*(k6*x18*x18 - k7*x21) + (-1)*k5*x21)/k19,
  diff(x22, t) = 0,
  diff(x23, t) = (1*k19*k12*x24*k21 + (-1)*k19*(k10*x23*x26 - k11*x25))/k19,
  diff(x24, t) = (-1)*k19*k12*x24*k21/k19,
  diff(x25, t) = 1*k19*(k10*x23*x26 - k11*x25)/k19 }