B'There was an electronic store heist last night. All keyboards which were in the store yesterday were numbered in ascending order from some integer number x . For example, if x = 4 and there were 3 keyboards in the store, then the devices had indices 4 , 5 and 6 , and if x = 10 and there were 7 of them then the keyboards had indices 10 , 11 , 12 , 13 , 14 , 15 and 16 . After the heist, only n keyboards remain, and they have indices a_1, a_2, ... , a_n . Calculate the minimum possible number of keyboards that have been stolen. The staff remember neither x nor the number of keyboards in the store before the heist. The first line contains single integer n (1 <= n <= 1 ,000) -- the number of keyboards in the store that remained after the heist. The second line contains n distinct integers a_1, a_2, ... , a_n (1 <= a_i <= 10^{9}) -- the indices of the remaining keyboards. The integers a_i are given in arbitrary order and are pairwise distinct. Print the minimum possible number of keyboards that have been stolen if the staff remember neither x nor the number of keyboards in the store before the heist. In the first example, if x=8 then minimum number of stolen keyboards is equal to 2 . The keyboards with indices 9 and 11 were stolen during the heist. In the second example, if x=4 then nothing was stolen during the heist. '...