reserve p,q,r for FinSequence;
reserve u,v,x,y,y1,y2,z for object, A,D,X,Y for set;
reserve i,j,k,l,m,n for Nat;

theorem
  <* u,v *> <> <* x,y,z *>
proof
  len<* u,v *> = 2 by FINSEQ_1:44;
  hence thesis by FINSEQ_1:45;
end;
