I try to use a different password for every site and I remember all the passwords I use. This is obviously not helpful to anybody and would be thoroughly imprac

I try to use a different password for every site and I remember all the passwords I use. This is obviously not helpful to anybody and would be thoroughly impractical even for me to rely on, because not everybody is good at remembering 18-30 character strings of letters, numbers and symbols, and equally I figure one day I will not have the same ability to remember them either. So I keep the de facto "ciphers" on paper. These ciphers usually take the form of differential equations that give fairly lengthy, rational numerical solutions. Equations have the advantage of not looking like a cipher, especially if you're known to be a mathematician. Even if I lost the paper or it was destroyed, the equations are memorable to me for having played a role in some of my studies a long time ago. I could root around in my notes and find them again. The equations are all I need to have on paper because I can just do the math and remember how I form the solution into a password to include letters and symbols. Even if I forgot how exactly I formed the solution, with the numerical string resolved I could quite simply brute force the few characters remaining. I keep this bit of paper safe but separate to my credit cards and cash because that's the most likely thing to be stolen from me. But you know what? I don't even consider this a particularly secure solution. It's just more fun. And it has to be better than storing passwords with a password manager, using a pen drive or keeping passwords themselves on paper.