#include <bits/stdc++.h>

#define EQ(a,b) (fabs(a - b) <= fabs(a + b)*EPS)

using namespace std;

bool Check(const map<int, int> & stor)
{
    int lichy = 0;
    for(auto i : stor)
    {
        if(i.second%2 == 1)
        {
            if(lichy >= 1)
                return false;
            else
            {
                lichy++;
            }
            
        }
    }

    return true;
}

struct Val
{
    map<int, int> m_Stor;
    int start;
    int end;

    Val(const map<int, int> & src, int s, int e)
    {
        m_Stor = src;
        start = s;
        end = e;
    };
};

int Solve(const string & input)
{
    map<int, int> stor;
    
    for(auto i : input)
    {
        stor[i - 'a']++;
    }

    queue<Val> q;
    q.push({stor, 0, int( input.size()) - 1});

    while(! q.empty())
    {
        auto & cur = q.front();
        
        if( cur.start < cur.end && cur.end >= 0 && cur.start < (int)input.size())
        {
            if(Check(cur.m_Stor))
                return cur.end - cur.start + 1;
            
            cur.m_Stor[input[cur.start] - 'a']--;
            q.push({cur.m_Stor, cur.start + 1, cur.end});
            cur.m_Stor[input[cur.start] - 'a']++;


            cur.m_Stor[input[cur.end] - 'a']--;
            q.push({cur.m_Stor, cur.start, cur.end-1});
        }


        q.pop();
    }

    return 1;
}

int main()
{
    ios::sync_with_stdio(false);


    int len;
    string input;
    cin >> len >> input;

    //cout << len << " " << input << endl;

    cout << Solve(input) << endl;
    

    return 0;
}