#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pii = pair<int,int>;
using vi = vector<int>;

#define fastio ios::sync_with_stdio(false); cin.tie(nullptr);
#define all(x) (x).begin(), (x).end()

int main() {
    fastio;

    int ans = 1;
    bool found = false;
    int temp ;
    for(int i=1;i<=9;i++){
      cin >> temp;
      
      if(!found && temp != i){
         ans = i;
         found = true;
        }
    }
    if(!found) ans = 10;
    cout << ans ;

    return 0;
}