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

using ll = long long;
using vi = vector<int>;
using vc = vector<char>;
using vs = vector<string>;
using vll = vector<ll>;

#define int long long
#define f first
#define s second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define foo(i, a, b) for (int i = (a); i < (b); ++i)
#define rfoo(i, a, b) for (int i = (a); i >= (b); --i)
#define input(v)      \
    for (auto &x : v) \
    cin >> x
#define print(v)          \
    for (auto x : v)      \
        cout << x << " "; \
    cout << '\n'
#define yes cout << "YES" << std::endl;
#define no cout << "NO" << std::endl;
#define nl cout << "\n";

const int MOD = 1e9 + 7;
const ll INF = 1e18;

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }

ll power(ll a, ll b)
{
    ll res = 1;
    while (b)
    {
        if (b & 1)
            res *= a;
        a *= a;
        b >>= 1;
    }
    return res;
}

ll modexp(ll a, ll b, ll mod = MOD)
{
    ll res = 1;
    a %= mod;
    while (b)
    {
        if (b & 1)
            res = (res * a) % mod;
        a = (a * a) % mod;
        b >>= 1;
    }
    return res;
}

ll modmul(ll a, ll b, ll mod = MOD)
{
    return ((a % mod) * (b % mod)) % mod;
}

bool isprime(int n)
{
    if (n < 2)
        return false;
    for (int i = 2; i * i <= n; ++i)
        if (n % i == 0)
            return false;
    return true;
}

void sieve(int n, vector<bool> &isPrime)
{
    isPrime.assign(n + 1, true);
    isPrime[0] = isPrime[1] = false;
    for (int i = 2; i * i <= n; ++i)
        if (isPrime[i])
            for (int j = i * i; j <= n; j += i)
                isPrime[j] = false;
}

int getbit(ll n, int b) { return (n >> b) & 1; }
ll setbit(ll n, int b) { return n | (1LL << b); }
ll resetbit(ll n, int b) { return n & ~(1LL << b); }
ll togglebit(ll n, int b) { return n ^ (1LL << b); }
bool ispoftwo(ll n) { return n > 0 && !(n & (n - 1)); }
int countSetBits(ll n) { return __builtin_popcountll(n); }

int digitCount(ll n, int base = 10)
{
    return n ? (int)(log(n) / log(base)) + 1 : 1;
}

vi factors(int n)
{
    vi res;
    for (int i = 1; i * i <= n; i++)
    {
        if (n % i == 0)
        {
            res.pb(i);
            if (i != n / i)
                res.pb(n / i);
        }
    }
    sort(all(res));
    return res;
}

#define lb(v, x) (lower_bound(all(v), x) - (v).begin())
#define ub(v, x) (upper_bound(all(v), x) - (v).begin())
#define count_occ(v, x) (ub(v, x) - lb(v, x))

#define fastio                   \
    ios::sync_with_stdio(false); \
    cin.tie(nullptr);            \
    cout.tie(nullptr)

signed main()
{
    fastio;

    int t = 1;
    // cin >> t;
    while (t--)
    {
        vi v(9);
        input(v);

        ll sum=0;
        ll su = 0;
        foo(i,0,10) {
            su+=i+1;
        }

        foo(i,0,9) {
            sum += v[i];
        }
        cout<<su-sum;

    }
}


// string a,b,c;
//         cin>>a;
//         cin>>b;
//         cin>>c;
//         swap(a[0],a[2]); swap(a[1],a[2]);
//         swap(b[1],b[2]);
//         reverse(c.begin(),c.end());

//         cout<<a[0] << " " << a[1] << " "<<a[2];
//         nl
//         cout<<b[0] << " " << b[1]<< " "<< b[2];
//         nl
//         cout<<c[0] << " " << c[1] << " " << c[2];