#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;
string s;
bool done[N];
int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> s;
    done[0] = true;
    for(int i = 0;i < s.size();i++) {
		if(i + 2 < s.size()) {
			int cur = stoi(s.substr(i, 3));
			if(cur <= n && cur == 100) {
				i += 2;
				done[cur] = true;
				continue;
			}
		}
		if(i + 1 < s.size()) {
			int cur = stoi(s.substr(i, 2));
			if(cur <= n && !done[cur]) {
				i++;
				done[cur] = true;
				continue;
			}
		}
		done[s[i] - '0'] = true;
	}
	for(int i = 1;i <= n;i++)
		if(!done[i])
			return cout << i, 0;
    return 0;
}