Kattis has many pairs of nice, warm, knit socks in her sock drawer that are perfect for the winter. These socks come in a wide range of colours and types, and have all been mixed together. Each morning Kattis needs to pick two matching socks.</p>

To find matching socks, she simply randomly takes single socks out of the drawer until she has a matching pair. It may take a long time, for example when she keeps drawing right socks without a matching left one. How long does she need to keep drawing socks until she is guaranteed to have a pair to wear?

입력 형식

The input consists of:</p>

• One line with an integer $n$ ($1 \leq n \leq 1\,000$), the number of groups of identical socks.
• $n$ lines, each describing a group of identical socks with the following:
  • A string $i$, the type of the socks in the group. The type $i$ consists of between $1$ and $20$ lowercase English letters. Socks with the same type are considered compatible for fashion purposes.
  • A string $j$, the fit of the socks in the group, which is either left, right or any, indicating whether the socks fit on the left foot, the right foot or any foot.
  • An integer $k$ ($1\leq k \leq 1\,000$), the number of socks in the drawer that are of this type and fit.
  </li> </ul>

  A given fit of a given type of sock appears at most once in the input.

  출력 형식

  Output the minimum number of socks Kattis needs to draw to be guaranteed to get a matching pair. If it is not possible to get a matching pair at all, output impossible.

  예제 입력 1

  3
  fuzzy any 10
  wool left 6
  wool right 4

  예제 출력 1

  8

  예제 입력 2

  3
  sports any 1
  black left 6
  white right 6

  예제 출력 2

  impossible

  예제 입력 3

  2
  warm any 5
  warm left 3

  예제 출력 3

  4