Marshrutkas#187
In a modern city, private minibuses play an important role in transportation. The city has a known number of routes and total stops. Some stops may be shared by several routes, allowing passengers to transfer as needed. Your task is simple: determine the minimum number of transfers required to travel from stop to stop .
The first line contains two numbers: the number of minibus stops in the city, (2 \le N \le 100\,000), and the number of routes, (1 \le M \le 20). Each of the following lines describes a route. Each line begins with the number of stops on the route, (2 \le K_i \le 50), followed by the stop numbers for this route. The last line contains two numbers: the starting stop and the destination stop .
Output the minimum number of transfers needed to get from stop to stop . If it is impossible to reach stop from stop using only minibuses, output Call a taxi!.
Example 1