Common ancestor

The DNA sequence for every living creature in Berland can be represented as a non-empty line consisting of lowercase Latin letters. Berland scientists found out that all the creatures evolve by stages. During one stage exactly one symbol of the DNA line is replaced by exactly two other ones. At that overall there are n permissible substitutions. The substitution a_i->b_ic_i means that any one symbol a_i can be replaced with two symbols b_ic_i. Every substitution could happen an unlimited number of times.

They say that two creatures with DNA sequences s₁ and s₂ can have a common ancestor if there exists such a DNA sequence s₃ that throughout evolution it can result in s₁ and s₂, perhaps after a different number of stages. Your task is to find out by the given s₁ and s₂ whether the creatures possessing such DNA sequences can have a common ancestor. If the answer is positive, you have to find the length of the shortest sequence of the common ancestor’s DNA.

The first line contains a non-empty DNA sequence s₁, the second line contains a non-empty DNA sequence s₂. The lengths of these lines do not exceed 50, the lines contain only lowercase Latin letters. The third line contains an integer n (0 ≤ n ≤ 50) — the number of permissible substitutions. Then follow n lines each of which describes a substitution in the format a_i->b_ic_i. The characters a_i, b_i, and c_i are lowercase Latin letters. Lines s₁ and s₂ can coincide, the list of substitutions can contain similar substitutions.

If s₁ and s₂ cannot have a common ancestor, print -1. Otherwise print the length of the shortest sequence s₃, from which s₁ and s₂ could have evolved.

ababa
aba
2
c->ba
c->cc

2

ababa
aba
7
c->ba
c->cc
e->ab
z->ea
b->ba
d->dd
d->ab

1

ababa
aba
1
c->ba

-1