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If $p$ is a prime of size 5 or greater then it is not good. If $p$ does not equal 7 then $7/p^{2}$ has to be represented by a parallel circuit of size two with two parallel elements of the form $a/p$ and $b/p$ with $a$ and $b$ less than $p$ hence it must be of the form $1-ab/p^{2}$ with $a$ and $b$ less than $p$ but $ab$ must be less than $(p-1)(p-1)$ but then smallest value that can be so expressed is $2p-1/p^{2}$ which if $p$ is size 5 or greater is larger than 7 and we have a contradiction and we are done except for the case $p=7$.. If $p$ equals 7 then 5/49 has to be represented by a parallel circuit of size 2 of elements of the form $a/7$ and $b/7$ where $a$ and $b$ are less than 7 hence it must be of the form $1-(ab/49)$ with $a$ and $b$ less than 7 but the smallest value that can be so expressed is 13 and we have a contradiction and we are done.