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




void solve() {
    
    int n = 9 ;



    vector<int>arr(n);

    for(auto &a : arr) cin >>a ;



    int nm = (10 * (10 +1)) /2;

    int ans= accumulate(arr.begin() , arr.end() , 0LL);

    cout << nm - ans;


//    cout<< nm - accumulate(arr.begin() , arr.end() , 0LL);







}

signed main() {

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
        cout<<endl;
    }
    return 0;
}