#include <iostream>
#include <string>

using namespace std;

static void setup()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
}

static void run()
{
    static const int kExpectSum = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9+ 10;
    auto sum = 0;
    for (auto i = 0; i < 9; ++i) {
        int b;
        cin >> b;
        sum += b;
    }

    cout << kExpectSum - sum << endl;
}

int main(int argc, char **argv)
{
    setup();
    run();
    return 0;
}