#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;
const int N = 1e5 + 5;
int n, cnt[10], f[10];
string s;
int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> s;
	for(int i = 1;i <= n;i++) {
		string cur = to_string(i);
		for(auto j : cur)
			cnt[j - '0']++;
	}
	for(auto i : s)
		f[i - '0']++;
	vector<int> v;
	for(int i = 0;i <= 9;i++) {
		if(f[i] != cnt[i])
			v.push_back(i);
	}
	if(v.size() == 1) {
		if(cnt[v[0]] - f[v[0]] != 1)
			cout << v[0];
		return cout << v[0], 0;
	}
	if(v[0] == 0) {
		cout << v[1];
		if(cnt[0] - f[0] != 1)
			cout << "0";
		cout << "0";
		return 0;
	}
	if(cnt[v[0]] - f[v[0]] < cnt[v[1]] - f[v[1]])
		swap(v[0], v[1]);
	cout << v[0] << v[1];
    return 0;
}