Hello. Does anyone know a equation for setting up a 3 street bet size geometry so that on the river we end up with 1spr?

My coach gave me a 2 street equation which is basically.

(Villains stacks size-Current pot size)/3

So if pot is 20bb OTF and villain has 90BB remaining we do the following.

90-20=70/3=~23 so then if we bet 23bb on the flop, the pot is now 66bb and villain has 67bb remaining, a perfect 1spr.

But he is unsure about a 3street equation.

Please help if you know this or can figure it out lol