Phyllis works for a large, multi-national corporation. She moves from department to department where her job is to uncover and remove any redundancies inherent in the day-to-day activities of the workers. And she is quite good at her job.</p>

During her most recent assignment, she was given the following chart displaying the chain of command within the department:

Figure 1

Whenever anyone needs to send a report to their bosses, they use the above chart, sending one report along each arrow. Phyllis realized almost instantly that there were redundancies here. Specifically, since D sends a report to B and B sends a report to A, there’s really no need for D to send a report to A directly, since it will be summarized in the report B sends to A. Thus the connection from D to A can be removed. If there had also been a connection from C to B, then the connections from D to B and C to A could have been removed as well.

Phyllis would like your help with this. Given a description of a chart like the one above, she would like a program that identifies all connections that can be removed from the chart.

입력 형식

The first line of each test case will contain a positive integer m indicating the number of connections in the chart. Following that will be m lines each containing two strings s₁ s₂ indicating that there is a connection from employee s₁ to his/her boss s2. In any test case there will be no more than 200 employees listed and no connection will appear more than once. A line containing a single 0 will terminate the input.

출력 형식

For each test case, output the number of connections that should be removed followed by a list of the deleted connections in lexicographic order. Connection s₁ s₂ should be represented by the string s1,s2.

예제 입력

5
D B
D C
D A
B A
C A
6
D B
D C
D A
C B
B A
C A
1
Danny Tessa
0

예제 출력

Case 1: 1 D,A
Case 2: 3 C,A D,A D,B
Case 3: 0