Time Limit: 1000 ms Memory Limit: 65536 KiB
Given several formula like "variable1 relation variable2", where relation may be <,<=,=,!=,>=,>, variables may contain up to 10 letters or digits and are case-sensitive. Please determine whether there is a conflict.
There are several cases. Each case begins with a line "Case%n:"(%n is the case number), and contains several formulas, one per line. There are no more than 100 formulas for each case. Please see sample input for more details. Input is teminated by EOF.
If there is no conflict, output"YES", otherwise, output"NO". Please refer to sample output for the exact output format.
Case1: xyz < 123 123 < 45 Case2: x < y y < x
Case1: YES Case2: NO