program var_27_task_2;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils;

var
    I : integer;
    SumOfNumbers : integer;
    N : integer;

begin
    N := 0;
    While N <= 0 do
    begin
        try
            WriteLn('Enter the value of n : ');
            ReadLn(N);
        except
        on E: Exception do
            Writeln(E.ClassName, ': ', E.Message);
    end;

    if N<=0 then
        begin
            WriteLn('Input Error. Check if the data is correct.');
        end;
    end;

    for I := 1 to N do
        SumOfNumbers := SumOfNumbers + ((I-1)+I);

    WriteLn('Sum of all numbers = ', SumOfNumbers);
    Writeln('Press <enter> to quit...');
    Readln;
end.