BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));

        String numberString = buffer.readLine();
        int number = Integer.parseInt(numberString);
        int count = 0;
        int sum;

        while (true)
        {
            String s = buffer.readLine();
            if (s.equals("сумма")) {
                break;
                System.out.println(sum);
            }
            else {
                sum = number + count;
                count = number;
            }

        }