Var
 N,i:Integer;
 flag,flag1:boolean;
 A:Array[1..100] of Integer;
 f:Text;
 S:String;

Begin
 Writeln('Enter the string: ');
 Readln(S);
 Assign(f,'fff.txt');
 Rewrite(f);
 Write(f,S);
 Close(f);
 Reset(f);
 N:=0;
 Repeat
  Inc(N);
  Read(f,A[N]);
 Until EoF(f);
 Close(f);
 Erase(f);
 writeln;
 i:=0;
 flag1:=false;
 flag:=true;
 Repeat
  Inc(i);
  repeat
   if (A[i+1]-A[i])=(A[i+2]-A[i+1]) then
    begin
     flag1:=true;
     if flag then
      begin
       write(A[i],' ',A[i+1],' ',A[i+2]);
       flag:=false;
      end
     else
      write(' ',A[i+2]);
     if i<N-2 then Inc(i);
    end;
  until (i>=N-2) or ((A[i+1]-A[i])<>(A[i+2]-A[i+1]));
  if i<N-2 then
   begin
    if flag1 then
     begin
      writeln;
      flag1:=false;
     end;
    flag:=true;
   end;
 Until i>=N-2;
 Readln
End.