CF1041A.Heist

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 $a_1, a_2, \dots, a_n$. 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.

昨晚发生了一起电子商店盗窃案。

昨天店内所有的键盘都按升序编号，起始编号为某个整数 $x$。例如，若 $x = 4$ 且店内共有 $3$ 个键盘，则这些设备的编号分别为 $4$、$5$ 和 $6$；若 $x = 10$ 且共有 $7$ 个键盘，则键盘编号分别为 $10$、$11$、$12$、$13$、$14$、$15$ 和 $16$。

盗窃之后，仅剩 $n$ 个键盘，其编号为 $a_1, a_2, \dots, a_n$。请计算可能被盗键盘的最小数量。店员既不记得初始编号 $x$，也不记得盗窃前店内键盘的总数。

The first line contains single integer $n$ $(1 \le n \le 1\,000)$ — the number of keyboards in the store that remained after the heist.

The second line contains $n$ distinct integers $a_1, a_2, \dots, a_n$ $(1 \le a_i \le 10^{9})$ — the indices of the remaining keyboards. The integers $a_i$ are given in arbitrary order and are pairwise distinct.

第一行包含一个整数 $n$ $(1 \le n \le 1\,000)$ —— 表示盗窃事件后商店中剩余的键盘数量。

第二行包含 $n$ 个互不相同的整数 $a_1, a_2, \dots, a_n$ $(1 \le a_i \le 10^{9})$ —— 表示剩余键盘的编号。这些整数 $a_i$ 以任意顺序给出，且两两不同。

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.

如果工作人员既不记得 $x$，也不记得盗窃发生前商店中的键盘数量，那么请输出可能被盗的键盘的最少数量。

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.

在第一个例子中，若 $x=8$，则被窃键盘的最小数量为 $2$。盗窃事件中被窃的键盘编号为 $9$ 和 $11$。

在第二个例子中，若 $x=4$，则盗窃事件中没有任何键盘被窃。