#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned u;
typedef vector<int> vi;
typedef pair<int, int> pii;
#define F first;
#define S second;
#define PB push_back;
#define MP make_pair;

bool EQ(double a, double b) {
    return (fabs(a-b) / (a+b) < DBL_EPSILON);
}

vector<char> arr ;
bool isValid (vector<int> & letters ) {
    bool uni = false ;
    for ( auto & it : letters ) {
        if ( it % 2 == 1 ){
            if ( uni == true )
                return false;
            else
                uni = true ;
        }
    }
    return true ;
}

bool hasLen ( ll len ) {
    vector<int> letters ( 30 , 0 );
    for ( ll i = 0 ; i < len ; ++ i ){
        char l = arr[i] ;
        letters[l-'a'] += 1 ;
    }
    if ( isValid( letters ) ) return true ;
    for ( ll i = len ; i < arr.size() ; ++ i ) {
        char l = arr[i] ;
        letters[l-'a'] += 1 ;
        letters[ arr[i - len] - 'a' ] -= 1 ;
        if ( isValid( letters ) ) return true ;
    }
    return false ;
}

int main( ) {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    // code

    ll n ; cin >> n ;
    for ( ll i = 0 ; i < n ; ++ i ){
        char tmp ; cin >> tmp ;
        arr.push_back(tmp);
    }

    for ( ll i = n; i > 0; --i) {
        if (hasLen(i)) {
            cout << i;
            break;
        }
    }

    return 0;
}