Making a customizable LCG that travels backward and forward

How would i go about making an LCG (type of pseudo random number generator) travel in both directions? I know that travelling forward is (a*x+c)%m but how would i be able to reverse it? I am using this so i can store the seed at the position of the player in a map and be able to generate things around it by propogating backward and forward in the LCG (like some sort of randomized number line).