# include <bits/stdc++.h>
using namespace std;
int n;
string s;
bool check(int mid){
unordered_set <string> hash;
for (int i = 0;i + mid - 1 < n;i ++ ){
string str = s.substr(i,mid);
if (hash.count(str)) return false;
else hash.insert(str);
}
return true;
}
int main(){
cin >> n >> s;
int l = 1,r = n;
while (l < r) {
int mid = l + r >> 1;
if (check(mid)) r = mid;
else l = mid + 1;
}
cout << l << endl;
return 0;
}