#include <bits/stdc++.h>

using namespace std;

//#define int long long
#define ld long double
#define el '\n'
#define fi first
#define se second

#define Nine_seconds ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);


void run_case(int tc) {
    int n;
    string s;

    cin >> n >> s;
    int lst = 0;
    for (int i = 0; i < s.size(); i++) {
        if (i < 9 && s[i] - '0' != lst + 1)
            return cout << lst + 1, void();
        else if (i >= 9) {
            int num = (s[i] - '0') * 10 + (s[i + 1] - '0');
            if (num != lst + 1)
                return cout << lst + 1, void();
        }
        lst++;
    }
}


int32_t main() {
    Nine_seconds        /*Turn Off for Interactive Problems*/

    int _t = 1;
    //cin >> _t;
    for (int i = 1; i <= _t; i++) {
        run_case(i);
    }
}