P6681 [CCO 2019] Bad Codes

There are $N$ strings, each of length at most $M$. The strings can be concatenated in any way. If it is possible to obtain two identical strings by concatenating strings in two different ways, output the minimum possible length of such a string. Otherwise, output `-1`.

The first line contains two integers $N, M$. The next $N$ lines each contain one string of length at most $M$.

If it is possible to obtain two identical strings by concatenating strings in two different ways, output the minimum possible length of such a string. Otherwise, output `-1`.

#### Explanation for Sample 1. Concatenating the second string and the third string can produce the first string. #### Constraints For $100\%$ of the testdata, it is guaranteed that $1 \le N, M \le 50$. None of the input strings is empty, and every input character is in $\{0,1\}$. | Subtask | $N=$ | $M\le$ | Special restriction | Score | | :-: | :-: | :-: | :-: | :-: | | 1 | $4$ | $6$ | None. | $16$ | | 2 | No special restrictions. | No special restrictions. | Each string contains exactly one `1`, such as `00100`. | $28$ | | 3 | No special restrictions. | No special restrictions. | None. | $56$ | #### Notes This problem is translated from [Canadian Computing Olympiad 2019](https://cemc.math.uwaterloo.ca/contests/computing/2019/index.html) [Day 2](https://cemc.math.uwaterloo.ca/contests/computing/2019/stage%202/day2.pdf) T3 Bad Codes. Translated by ChatGPT 5