/**
 * Common Substring - Three String Values
 * The program must accept three string values S1, S2 and S3 as the input.
 * The program must print the longest common substring in S1, S2 and S3.
 * If there are two or more longest common substring values, the program must print the first occurring longest common substring.
 * If there is no such longest common substring, the program must print -1 as the output.
 *
 * Boundary Condition(s):
 * 2