function IsOperator(const ch: Char): Boolean;
begin
  Result := (ch = '+') or (ch = '-') or (ch = '*') or (ch = '/') or (ch = '^');
end;

function GetPrecedence(const op: Char): Integer;
begin
  case op of
    '+', '-': Result := 1;
    '*', '/': Result := 2;
    '^': Result := 3;
  else
    Result := 0;
  end;
end;

function ConvertToRPN(const expression: string): string;
var
  stack: string;
  output: string;
  i: Integer;
  ch: Char;
begin
  stack := '';
  output := '';

  for i := 1 to Length(expression) do
  begin
    ch := expression[i];
    if ch in ['A'..'Z', 'a'..'z'] then
    begin
      output := output + ch;
    end
    else if ch in ['0'..'9'] then
    begin
      output := output + ch;
    end
    else if IsOperator(ch) then
    begin
      while (Length(stack) > 0) and IsOperator(stack[Length(stack)]) and (GetPrecedence(stack[Length(stack)]) >= GetPrecedence(ch)) do
      begin
        output := output + ' ' + stack[Length(stack)];
        Delete(stack, Length(stack), 1);
      end;
      stack := stack + ch;
    end
    else if ch = '(' then
    begin
      stack := stack + ch;
    end
    else if ch = ')' then
    begin
      while (Length(stack) > 0) and (stack[Length(stack)] <> '(') do
      begin
        output := output + ' ' + stack[Length(stack)];
        Delete(stack, Length(stack), 1);
      end;
      // Remove the '(' from the stack
      Delete(stack, Length(stack), 1);
    end;
  end;

  // Pop any remaining operators from the stack to the output
  while Length(stack) > 0 do
  begin
    output := output + ' ' + stack[Length(stack)];
    Delete(stack, Length(stack), 1);
  end;

  Result := output;
end;