#include <bits/stdc++.h>

using namespace std;

#define fio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define next uhfsdhfhsdufhsdsdhfhiosdhodf
#define back rerererwrwerwerwerwewer

typedef long long ll;

int main() { fio
    int n;
    cin >> n;
    string s;
    cin >> s;
    string needle = s;
    reverse(needle.begin(),needle.end());
    vector<ll> next(needle.size()+1,-1);
    for (ll i = 0; i < needle.size(); i++){
        ll back = next[i];
        while (back >= 0 && needle[back] != needle[i])
            back = next[back];
        next[i+1] = back+1;
    }
    vector<ll> res;
    ll pos = 0;
    for (ll i = 0; i < s.size(); i++){
        while (pos >= 0 && needle[pos] != s[i])
            pos = next[pos];
        pos++;
    }
    cout << n-pos << '\n';
    return 0;
}