What do you see, when you have the public key ?
What do you see here?
3+2= 5, 3*2= 6, 6/3= 2, 2-3= 1, 3-2= -1. Now we have public key of 1, 2, 3, 4, 5, 6. Add, divide, subtract and multiply, it all works the same whether you do it with public keys of the private keys, or you just do them directly with private keys.
In other words, if you have the public key of private key 89, then by having 1 up to 9 public keys saved, you could solve the private key after subtracting G 80 times from 89, when you reach public key of 9 after 80 steps then you know the target's value. It works the same with multiplying, dividing etc.