#include <bits/stdc++.h>
#define rep(i,a,b) for(int i = (a); i < (b); i++)
#define all(A) (A).begin(),(A).end()
#define MOD 1000000007
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;

int main() {
	set<int> S;
	rep(i,0,9){
		int b; cin >> b;
		S.insert(b);
	}
	rep(i,1,11){
		if(!S.count(i)){
			cout << i << endl;
			return 0;
		}
	}
}