begin

  integer  divideresult;

  procedure  divide ( y, z )
  begin

    divideresult := y / z;

  end;


  integer  sum2result;

  procedure  sum2 ( y, z )
  begin

    sum2result := y + z;

  end;


  integer  average4result;

  procedure average4 ( w, x, y, z )
  begin

    integer  sum4result;

    procedure  sum4 ( w, x, y, z )
    begin

      integer  sum3result;

      procedure  sum3 ( x, y, z )
      begin

        call sum2 ( y, z );

        call sum2 ( x, sum2result );

        sum3result := sum2result;
        
      end;

      call sum3 ( x, y, z );

      call sum2 ( w, sum3result );

      sum4result := sum2result;
      
    end;

    call sum4 ( w, x, y, z );

    call divide ( sum4result, 4 );

    average4result := divideresult;
    
  end;


  integer  w, x, y, z;

  read ( w, x, y, z );
  call average4 ( w, x, y, z );
  write ( average4result );

end