#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

#define el '\n'
#define FIO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef unsigned uint;
typedef __int128 bint;
typedef long double ld;
typedef complex<ld> pt;
typedef unsigned long long ull;

template<typename T, typename X>
using hashTable = gp_hash_table<T, X>;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

// mt19937_64 for unsigned long long
mt19937 rng(std::chrono::system_clock::now().time_since_epoch().count());
const int mod = 998244353, N = 1e5 + 5;

void doWork()
{
    int n;
    cin >> n;

    int num = 1;
    string str;
    cin >> str;
    reverse(str.begin(), str.end());
    while(!str.empty())
    {
        string t = to_string(num);
        string s = "";
        if((int) str.size() < (int) t.size())
        {
            cout << num << '\n';
            return;
        }
        while((int) s.size() < (int) t.size())
        {
            s += str.back();
            str.pop_back();
        }

        if(s != t)
        {
            cout << num << '\n';
            return;
        }
        num += 1;
    }
    assert(false);
}

signed main()
{
    FIO
    int T = 1;
//    cin >> T;
    for(int i = 1; i <= T; i++)
        doWork();
}