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

int main()
{
    int arr[9];
    for (int i = 0; i < 9; i++)
    {
        cin >> arr[i];
    }
    if (arr[0] == 2)
    {
        cout << 1 << endl;
        return 0;
    }
    
    for (int i = 0; i < 9; i++)
    {
        if (arr[9] == 9)
        {
            cout << 10 << endl;
            return 0;
        }
        if ((arr[i + 1] - arr[i]) != 1)
        {
            cout << arr[i] + 1;
            break;
        }
    }
    return 0;
}