// pec.cpp : This file contains the 'main' function. Program execution begins and ends there.
//
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <iomanip>
#include <set>
#include <string>
using namespace std;
int main()
{
int n;
cin >> n;
string s;
cin >> s;
int maxdif = 0;
for (int i = 0; i < n; i++)
{
vector<int>frek(26, 0);
for (int j = i; j < n; j++)
{
frek[s[j] - 'a'] += 1;
int maxi = 0;
int mini = 1000000036;
for (int k = 0; k < 26; k++)
{
maxi = max(maxi, frek[k]);
if (frek[k] > 0)
{
mini = min(mini, frek[k]);
}
}
/*cout << i << ' ';
cout << j << " maxi a mini su ";
cout << maxi << ' ';
cout << mini << endl;*/
maxdif = max(maxdif, maxi - mini);
}
}
cout << maxdif << endl;
return 0;
//std::cout << "Hello World!\n";
}
// Run program: Ctrl + F5 or Debug > Start Without Debugging menu
// Debug program: F5 or Debug > Start Debugging menu
// Tips for Getting Started:
// 1. Use the Solution Explorer window to add/manage files
// 2. Use the Team Explorer window to connect to source control
// 3. Use the Output window to see build output and other messages
// 4. Use the Error List window to view errors
// 5. Go to Project > Add New Item to create new code files, or Project > Add Existing Item to add existing code files to the project
// 6. In the future, to open this project again, go to File > Open > Project and select the .sln file
