#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <sstream>
#include <complex>
#include <algorithm>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <typeinfo>
#include <cassert>
#include <fstream>
#define REP(i,n) for(int i=0;i<n;i++)
#define FOR(i,a,b) for(int i = a;i<b;i++)
#define SSTR( x ) static_cast< std::ostringstream & >( \
        ( std::ostringstream() << std::dec << x ) ).str()
#define ALL(s) (s).begin(), (s).end()
using namespace std;
typedef long long unsigned int llu;
typedef long long ll;

int main (){
  string s;
  bool b = false;
  while (cin >> s){
    int last ;
    int next ;
    sscanf(s.c_str(),"%d",&next);
    if(next - last != 1){
      cout << last + 1 << endl ;
      b = true;
      break;
    }
    
    last = next;
  }
  if(!b) cout  << 10 << endl;
  return 0;
}