
theorem
  for X be set for x,y,z be Subset of X for q be FinSequence of BOOLEAN
  holds len MergeSequence(<*x,y,z*>,q) = 3
proof
  let X be set;
  let x,y,z be Subset of X;
  let q be FinSequence of BOOLEAN;
  thus len MergeSequence(<*x,y,z*>,q) = len <*x,y,z*> by Def1
    .= 3 by FINSEQ_1:45;
end;
