Polycarp loves lowercase letters and dislikes uppercase ones. Once he got a string s consisting only of lowercase and uppercase Latin letters.

Let A be a set of positions in the string. Let's call it pretty if following conditions are met:

• letters on positions from A in the string are all distinct（与众不同的） and lowercase（小写字母的）;
• there are no uppercase letters in the string which are situated between positions from A (i.e. there is no such j that s[j] is an uppercase letter, and a₁ < j < a₂ for some a₁ and a₂ from A).

Write a program that will determine（确定，下决心） the maximum number of elements(元素) in a pretty set of positions.

The first line contains a single integer n (1 ≤ n ≤ 200) — length of string s.

The second line contains a string s consisting of lowercase and uppercase Latin letters.

Print maximum number of elements in pretty set of positions for string s.

In the first example the desired positions might be 6 and 8 or 7 and 8. Positions 6 and 7 contain letters 'a', position 8 contains letter 'b'. The pair of positions 1 and 8 is not suitable because there is an uppercase letter 'B' between these position.

In the second example desired positions can be 7, 8 and 11. There are other ways to choose pretty set consisting of three elements.

In the third example the given string s does not contain any lowercase letters, so the answer is 0.

题目意思：求连续的小写子母中，种类最多的是多少种。

解题思路：利用set中存储的元素的唯一 性去重，第一次使用set，还是对set中的删除不是很熟悉，当时使用set的迭代器也就是一个个删除的

for(it=st.begin(); it!=st.end();)

     {

          st.erase(it++);

     }

实际上set中含有直接清空容器的函数clear().

 #include<cstring>

 #include<cstdio>

 #include<algorithm>

 #include<set>

 using namespace std;

 char s[];

 int main()

 {

     int n,i,sum,sum1;

     char a;

     sum=;

     sum1=;

     scanf("%d",&n);

     getchar();

     scanf("%s",s);

     set<char>st;

     set<char>::iterator it;

     for(i=; i<n; i++)

     {

         if(s[i]>='A'&&s[i]<='Z')

         {

             sum1=st.size();

             /*for(it=st.begin(); it!=st.end();)

             {

                 st.erase(it++);

             }*/

             st.clear();

             if(sum1>sum)

             {

                 sum=sum1;

             }

         }

         else if(s[i]>='a'&&s[i]<='z')

         {

             st.insert(s[i]);

         }

     }

     sum1=st.size();

     if(sum1>sum)

     {

         sum=sum1;

     }

     printf("%d\n",sum);

 }