1 + t * (4 - 5 * (-s1)))) + 
      t * ((14 * (-s1) - 11 + t * (4 - 5 * (-s1))) + t * (4 - 5 * 
          (-s1)))))) + (((-s2) + (t - 1) * (2 * (-s2) + (t - 1) * 
      (t - 1) * (-2 * (-s2) - (t - 1) * (-s2)))) + (t - 1) * ((2 * 
      (-s2) + (t - 1) * (t - 1) * (-2 * (-s2) - (t - 1) * (-s2))) + 
      (t - 1) * (((t - 1) + (t - 1)) * (-2 * (-s2) - (t - 1) * 
          (-s2)) - (t - 1) * (t - 1) * (-s2)))))/((-t) * ((-s1) + 
      (-t) * (2 * (-s1) + (-t) * (-t) * (-2 * (-s1) - (-t) * (-s1)))) + 
      (1