## Problem S5: Post's Correspondence Problem

Let A and B be two sequences of non-empty strings:
A = (a1, a2, ..., an), B = (b1, b2, ..., bn).
Let m be a positive integer. Does there exist a sequence of integers
i1, i2, ..., ik such that m > k > 0 and ai1ai2...aik = bi1bi2...bik?

For example, if A = (a, abaaa, ab) and B = (aaa, ab, b), then the required sequence of integers is (2,1,1,3) giving abaaaaaab = abaaaaaab.

### Input

The first two lines of input will contain m and n respectively, and m x n ≤ 40. The next 2n lines contain in order the elements of A followed by the elements of B. Each string is at most 20 characters.

### Output

If a solution exists, print k on a line by itself, followed by the integer sequence in order, one element per line. Otherwise, print a single line containing "No solution."

```7
3
a
abaaa
ab
aaa
ab
b```

```4
2
1
1
3```

```10
3
abc
def
ghi
jkl
mno
pqr```

### Sample Output 2

```No solution.
```

Point Value: 10
Time Limit: 10.00s
Memory Limit: 16M
Added: Sep 30, 2008

Problem Types: [Show]

Languages Allowed:
C++03, PAS, C, HASK, ASM, RUBY, PYTH2, JAVA, PHP, SCM, CAML, PERL, C#, C++11, PYTH3