#pragma GCC omptimize("unroll-loops")
#pragma GCC omptimize("игорь говно")
#pragma GCC optimize("no-stack-protector")
#pragma comment(linker, "/STACK:1000000000")

#include <iostream>
#include <cmath>
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <set>
#include <map>
#include <list>
#include <time.h>
#include <math.h>
#include <random>
#include <deque>
#include <queue>
#include <cassert>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <bitset>
#include <sstream>
#include <chrono>
    #define LOCAL
    #define fori(i, r, x) for(int i = r; i < x; i++)
    #define eb emplace_back
    #define lb lower_bound
    #define ub upper_bound
    #define er equal_range
    #define fi first
    #define se second

    using namespace std;

    typedef long long int lli;
    typedef long long ll;
    typedef long double ld;
    typedef pair<int, int> pii;
    typedef pair<ll,ll> pll;
    typedef pair<ld,ld> pld;
    typedef vector<int> vi;
    typedef vector<ll> vll;
    typedef vector<ld> vld;
    typedef vector<vector<int>> vvi;

    const int INF32 = 2009000999;
    const ll INF64 = 4e18;
    const int sz = 1e6;
    const int mod = 1e9+7;
    const long double EPS = 1e-18;
    const int base = 1000*1000*1000;
    const int p = 31;


    string s;
    ll cnt = 0, n;

    ll haash(string a) {
        long long hashh = 0, p_pow = 1;
        for (size_t i=0; i<a.size(); i++)  {
            hashh += (a[i] - 'a' + 1) * p_pow;
            p_pow *= p;
        }
        return hashh;
    }
    void step() {
        int st, stt;
        ll sttt = s[0];
        for(int i = n - 1; i >= 0; i--) {
            if (i == n - 1) {
                stt = s[i];
                s[i] = sttt;
            }

            else {
                st = s[i];
                s[i] = stt;
                stt = st;
            }

        }
    }
    ll b, c;
    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);

        #ifndef LOCAL
            freopen("input.txt", "r", stdin);
            freopen("output.txt", "w", stdout);
        #endif
        cin >> n;
        cin >> s;
        string s1(s);
        reverse(s1.begin(), s1.end());

        b = haash(s);
       // cerr << b << endl;
        c = haash(s1);
       // for(int i = 0; i < s.size() - 1; i++) step();

       // cerr << c << endl;
      //  cerr << haash(s) << endl;
        if (b == c) {
            cout << "0";
            return 0;
        }
        ll k = 0;
       // cerr << s << endl;
       // cerr << s1 << endl;
       //step();
     //cerr << s << endl;
        cnt = 0;
        ll ans = 0;
        for(int i = 0; i < s.size(); i++) {
            step();
           // cerr << s << endl;
            if (haash(s) == c) {
                ans = cnt + 1;
                cout << ans;
                return 0;
            }
            else if (haash(s) == b){
                cout << -1;
                return 0;
            }
            else {
                cnt++;
            }
        }

        cout << cnt;
        return 0;

    }