Longest Common Substring

A string $T = t_1 t_2 \dots t_m$ is a substring of a string $S = s_1 s_2 \dots s_n$ when there is an index $0 \le i \le n - m$ with $s_{i+1} s_{i+2} \dots s_{i+m} = T$. A substring is a run of consecutive characters cut out of $S$.

You are given two strings $A$ and $B$. Write a program that finds the length of the longest string that is a substring of $A$ and also a substring of $B$, together with the lexicographically smallest common substring of that length.

The first line has the string $A$ and the second line has the string $B$. Both strings consist of lowercase letters only, and the sum of the two lengths is at most 200,000.

Print the length of the longest common substring on the first line.

If that length is greater than 0, print on the second line the lexicographically smallest common substring of that length. If the two strings have no common substring, print only 0 and print no second line.