var elements: array of string[4]; //Globale Variablen
    a,b,count: integer;
    input:string;

procedure prepare;
begin
  count:=0;
  input:=form1.edit1.text;
  setlength(elements, 1);
  elements[0]:='';
end;

procedure fillarray;
var i:integer;
begin
  for i := 1 to length(input) do
    if input[i] = ','
      then begin
            count:=count+1;
            setlength(elements, count+1);
            elements[count] := '';
           end{then}
             else elements[count]:=elements[count] + input[i];
end;

function stringinteger(instring: string): boolean;
begin
  result:=strtointdef(instring,0)=strtointdef(instring,1);
end;


procedure TForm1.Button3Click(Sender: TObject);
var i,j:integer;
    step:boolean;
begin
  prepare;
  fillarray;
  step:=true;
  button1.Enabled:=true;
  button2.Enabled:=false;

  while step do
    for i := 0 to count do
      if stringinteger(elements[i]) = false
        then begin
           a:=strtoint(elements[i-2]);
           b:=strtoint(elements[i-1]);
           case elements[i][1] of  '+': a:=a+b;
                                   '-': a:=a-b;
                                   '*': a:=a*b;
                                   '/': a:=a div b;
                                   end;{case}
           elements[i-2]:=inttostr(a);
           for j := (i-1) to count do
           elements[j]:=elements[j+2];
           count:=count-2;
           step:=true;
           break;
      end{then}
      else
           step := false;
  label2.caption:=elements[0];
end;