在文件里面有n行数，每行不知道多少个，现在我们要求求出没两行的最长公共字串。-Within the files have n rows, each line don t know how many, now we ask for two ways haunted by the longest public string

Input question formats:

The first line a number N, says there are a N matrix

Each matrix after first by the two digital m, n, said the matrix is m* n matrix

Back row number is a n, m line