|
|||||||
|
Viruses
Binary Viruses Investigation Committee detected, that certain sequences of zeroes and ones are codes of viruses. The committee isolated a set of all the virus codes. A sequence of zeroes and ones is called safe, if any of its segments (i.e. sequence of consecutive elements) is not a virus code. The committee is aiming at finding, whether an infinite, safe sequence of zeroes and ones exists. ExampleFor a set of codes {011, 11, 00000}, the sample infinite safe sequence is 010101... . For a set of codes {01, 11, 00000} an infinite safe sequence of zeroes and ones does not exist. TaskWrite a program, which:
InputThe first line of the input file WIR.IN consists of one integer n standing for the number of all virus codes. Each of the next n lines consists of one non-empty word composed from 0s and 1s - a virus code. The total length of all words does not exceed 30000. OutputIn the first and the only line of the output file WIR.OUT one should find a word:
ExampleFor the input file WIR.IN: 3 01 11 00000 the correct result is the output file WIR.OUT: NIE |