CF611G New Year and Cake

Limak is a little polar bear. According to some old traditions, his bear family prepared a New Year cake. And Limak likes cakes. As you may know, a New Year cake is a strictly convex polygon with $ n $ vertices. Parents won't allow Limak to eat more than half of a cake because he would get sick. After some thinking they decided to cut a cake along one of $ n·(n-3)/2 $ diagonals. Then Limak will get a non-greater piece. Limak understands rules but he won't be happy if the second piece happens to be much bigger. Limak's disappointment will be equal to the difference between pieces' areas, multiplied by two. It can be proved that it will be integer for the given constraints. There are $ n·(n-3)/2 $ possible scenarios. Consider them all and find the sum of values of Limak's disappointment, modulo $ 10^{9}+7 $ .

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In the first sample possible values of Limak's disappointment are $ 0,18,18,24,30 $ .