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 Hello Ioannis. If I understand your problem correctly, you can achieve the result you need using the "Big M" method, though I think you may need to introduce some new integer variables ```Let E in {0, 1} binary M*E >= U M*E> = K ``` Where M is some "large" positive constant, though in this particular case it just needs to be greater than 6.  This will force E to be positive if either U or K is positive. D >= A + E - 1 This will require D to be positive if both A and E are positive.  Note that for this to work the objective must prefer to drive D to zero if possible, which typically turns out to be the case.  If not then you will need to add complementary constraints to drive D to zero if the conditions are not met. On 28/03/2015 3:00 am, address@hidden wrote: ```Good evening to every one, I have a problem in modelling the following situation: Let U, K in {-6, .. , 6} integers Let A in {0, 1} binary Let D in {0, 1} binary What I want to do is to model the condition: D = 1, iff (U > 0 OR K > 0) AND A = 1 Otherwise, D should equal 0. I can not figure out how to model this situation. Can any one give me an answear or even a hint? It would be very welcome. Thanks a lot``` ```-- Norman Jessup ```