#include <bits/stdc++.h>

using namespace std;

#define FOR(a, b, c) for(int a = (b); a < (c); a++)

using ll = long long;
#define LL long long

int main() 
{
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int n;
    cin >> n;

    string s;
    cin >> s;

    vector <int> res(2 * n - 1, 0);

    int l = -1, r = -1;

    FOR(z, 0, 2 * n - 1)
    {
        int i = (z + 1) >> 1;
        int j = (z >> 1);
        int p = (i >= r ? 0 : min(r -  i, res[2 * (l + r) - z]));
        while(j + p + 1 < n && i - p - 1 >= 0)
        {
            if(!(s[j + p + 1] == s[i - p - 1]))
                break;
            p++;
        }
        if(j + p > r)
        {
            l = i - p;
            r = j + p;
        }
        res[z] = p;
    }

    int odp = n;

    FOR(z, 0, 2 * n - 1)
    {
        int i = (z + 1) >> 1;
        int j = z >> 1;

        if(j + res[z] == n - 1)
        {
            odp = min(odp, i - res[z]);
        }
    }

    cout << odp << "\n";
}