Two Function Conundrum

This is probably the easiest task of this problem set. To help you understand the task let us define two key functions: Let f(p,q) be the set of all integers x such that (p mod x + q mod x) >= x. For example: f(1,7) = {2,4,8} f(5,7) = {2,3,4,6,8,9,10,11,12} f(6,7) = {4,8,9,10,11,12,13} Let E(n) = number of integers {0,1,2, ... ,n-1} that are relatively prime to n. Given p and q, your task is t