assume we have the following lists...
How can i return max value of "id"?


e.g.
ia1 = 11
ia2 = 8
ia4 = 5
ib1 =7

id month
ia1 2
ia2 3
ia3 4
ia4 5
ia1 5
ia2 6
ib1 7
ib2 8
ib6 9
ia1 11