#include<bits/stdc++.h>
using namespace std;
const int N =2e5;
signed main(){
	int n;
	cin>>n;
	string s;
	cin>>s;
	int mex =1;
	int curMove=1;
	for(int i = 0 ;  i  <s.size();i++){
		if(curMove==1){
			if((s[i]-'0')!=mex){return cout<<mex , 0;}
				}
		else if (curMove==2){
			string tmp;
			tmp+=s[i];
			if(i+1 >=s.size()){
				return cout<<mex,0;
			}
			tmp+=s[i+1];
			if(stoi(tmp) !=mex) return cout<<mex, 0;
			i++;
		}
		else if (curMove==3){
			string tmp;
			tmp+=s[i];
			if(i+1 >=s.size()){
				return cout<<mex,0;
			}
			tmp+=s[i+1];
			if(i+2 >=s.size())
				return cout<<mex,0;
			tmp+=s[i+2];
			if(stoi(tmp) !=mex) return cout<<mex, 0;
			i++;
			i++;
		}
		mex++;
		if(mex>=10)curMove++;
		if(mex>=100)curMove++;
	}
	cout<<mex<<endl;
}