CF701C.They Are Everywhere

Sergei B., the young coach of Pokemons, has found the big house which consists of n flats ordered in a row from left to right. It is possible to enter each flat from the street. It is possible to go out from each flat. Also, each flat is connected with the flat to the left and the flat to the right. Flat number 1 is only connected with the flat number 2 and the flat number n is only connected with the flat number n - 1.

There is exactly one Pokemon of some type in each of these flats. Sergei B. asked residents of the house to let him enter their flats in order to catch Pokemons. After consulting the residents of the house decided to let Sergei B. enter one flat from the street, visit several flats and then go out from some flat. But they won't let him visit the same flat more than once.

Sergei B. was very pleased, and now he wants to visit as few flats as possible in order to collect Pokemons of all types that appear in this house. Your task is to help him and determine this minimum number of flats he has to visit.

年轻的宝可梦教练谢尔盖·B. 发现了一栋由 $n$ 套公寓组成的大型住宅楼，这些公寓从左到右排成一列。每套公寓均可直接从街道进入，也均可从公寓中走出。此外，每套公寓均与左侧和右侧的公寓相连：1 号公寓仅与 2 号公寓相连，$n$ 号公寓仅与 $n-1$ 号公寓相连。

每套公寓中恰好有一只某种类型的宝可梦。谢尔盖·B. 请求住户允许他进入各自的公寓以捕获宝可梦。经协商，住户们同意让他从街道进入某一套公寓，访问若干套公寓后，再从某一套公寓走出。但他们不允许他重复访问同一套公寓。

谢尔盖·B. 非常高兴，现在他希望以最少的访问公寓数量，收集到该住宅楼中出现的所有种类的宝可梦。你的任务是帮助他确定这一最小访问公寓数。

The first line contains the integer n (1 ≤ n ≤ 100 000) — the number of flats in the house.

The second line contains the row s with the length n, it consists of uppercase and lowercase letters of English alphabet, the i-th letter equals the type of Pokemon, which is in the flat number i.

第一行包含一个整数 $n$（$1 \leq n \leq 100\,000$）—— 表示该住宅楼中公寓的数量。

第二行包含一个长度为 $n$ 的字符串 $s$，由英文字母的大写和小写字母组成；其中第 $i$ 个字母表示第 $i$ 号公寓中宝可梦的种类。

Print the minimum number of flats which Sergei B. should visit in order to catch Pokemons of all types which there are in the house.

输出谢尔盖·B. 为捕捉到屋内所有种类的宝可梦所需访问的最少公寓数量。

In the first test Sergei B. can begin, for example, from the flat number 1 and end in the flat number 2.

In the second test Sergei B. can begin, for example, from the flat number 4 and end in the flat number 6.

In the third test Sergei B. must begin from the flat number 2 and end in the flat number 6.

在第一个测试中，谢尔盖·B. 可以例如从公寓号 1 开始，并在公寓号 2 结束。

在第二个测试中，谢尔盖·B. 可以例如从公寓号 4 开始，并在公寓号 6 结束。

在第三个测试中，谢尔盖·B. 必须从公寓号 2 开始，并在公寓号 6 结束。