Repetend length in 1/n This problem is based on non-terminating, repeating decimal points.
Let \$n\$ be any positive integer \$(n &gt; 1 \text{ and } n &lt; 10000)\$, say \$7\$. Then, \$1/n = 1/7 = 0.142857142857142857...\$
We see a pattern like, 0. 142857 142857 142857 ... 
In this, the 142857 part is always repeating, which has length of \$6\$. Or, if \$n = 11\$, then \$1/n = 1/11 = 0.0909090909090909...\$
Here the length of the pattern is 2. So, here goes the problem!
Task
Given a positive integer \$n\$, \$(n &gt; 1 \text{ and } n &lt; 10000)\$, find the length of pattern in \$1/n\$, if it's repeating. Otherwise, return any non-positive integer (e.g., cases: \$1/5, 1/94, 1/22\$).
Note that, the pattern should start just after the decimal point. Hint: \$1/22 = 0.04545454545454545454545\$.
Sample I/O

5 -&gt; -1
13 -&gt; 6
21 -&gt; 6
27 -&gt; 3
33 -&gt; 2
37 -&gt; 3
94 -&gt; -1
22 -&gt; -1
69 -&gt; 22
197 -&gt; 98
65 -&gt; -1
\$1/9979\$
\$1/9967\$

This is a code-golf, so the fewest bytes will win!
Jelly, 6 bytes
R⁵*%i1

Try it online!
Basically compute 10**[1..n] % n and get the 1-based index of 1.