Suppose I have an expression which is a collection of symbols and integers arbitrarily combined with `Plus` and `Times`. For example, `A = a + c (d - a b d) + e c (a + b) f + b - 1` or maybe `B = a + b a c d` (where `a`, `b`, `c`, `d`, `e`, `f` are all different symbols), although it could be longer and more complicated. I want to estimate the expression by reducing it to only the terms with zero or one symbol multiplied together because the symbols all represent small numbers, and I want a first-order approximation. E.g. Reduced A would be `Ar = a+b-1` and reduced B is `Br = a`. How can I automate this in Mathematica? Assume that any constants are stand-alone and don't have to be distributed.