for example:

product1, product2, product3,..,productn

then you can get that unique number from formula:

product_1_used * 2^0 + product_2_used * 2^1 + product_3_used * 2^3 + ... + product_n_used * 2^(n-1)

where ^ is a power operation, and

product_i_used is 1 if product i is in group, and 0 if this is not the case.

for example if you have: hammer, drill, wedge and you need to identify set (hammer, wedge), you will get number:

hamer_used * 2^0 + drill_used * 2^1 + wedge_used * 2^2 =

1*2^0 + 0*2^1 + 1*2^2 =

1 + 0 + 4 =

5.