#include <bits/stdc++.h>  
using namespace std;  

#define int long long  

signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

	int n;
	cin >> n;

	string s;
	cin >> s;

	s = s;

	int cnt[26] {};
	int mp[26] {};
	for (int i = n - 1; i >= 0; i--) {
		if (!cnt[s[i] - 'a']) {
			for (int j = 0; j < 26; j++) {
				if (cnt[j]) {
					mp[s[i] - 'a']++;
				}
			}
		}
		cnt[s[i] - 'a']++;
	}


	for (auto &c : s) {
		c = 'a' + mp[c - 'a'];
	}

	vector<string> a(n);
	for (int i = 0; i < n; i++) {
		a[i] = string(s.begin() + i, s.end());
	}

	sort(a.begin(), a.end());
	cout << a[n - 1] << "\n";

    return 0;
}