#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include<bits/stdc++.h>

using namespace std;
using namespace __gnu_pbds;

template<typename T>
using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
template<typename T>
using Matrix=vector<vector<T>>;

#define speed ios_base::sync_with_stdio(false),cin.tie(nullptr)
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define nl "\n"
#define ll long long int
#define vi vector<int>
#define vll vector<ll>
#define vb vector<bool>
#define vs vector<string>
#define vc vector<char>
#define vd vector<double>
#define sti stack<int>
#define stll stack<ll>
#define sts stack<string>
#define stc stack<char>
#define qi queue<int>
#define qll queue<ll>
#define qs queue<string>
#define qc queue<char>
#define pi pair<int,int>
#define pll pair<ll,ll>
#define vpi vector<pi>
#define vpll vector<pll>
#define beg begin()
#define end end()
#define pb(v) push_back(v)
#define len size()
#define ins(a) insert(a)
#define pop pop()
#define forn(x,n) for(ll i=x;i<n;++i)
#define fori(x,n) for(ll i=x;i<n;++i)
#define forj(y,m) for(ll j=y;j<m;++j)
#define rev(a) reverse(a.beg,a.end)
#define all(a) a.beg,a.end
#define sort(a) sort(all(a))
#define yesno(b) cout<<(b ? "YES\n" : "NO\n")
#define inputV(a){ forn(0,a.len) cin>>a[i];}
#define inputVp(a){ forn(0,a.len) cin>>a[i].first>>a[i].second;}

signed main()
{
    speed;

    // ll T;
    // cin>>T;

// #ifndef OJ
    // freopen("input.txt", "r", stdin);
    // freopen("output,txt","w",stdout);
// #endif

    // while(T--)
    // {
        
    // }

    vll a(9);
    inputV(a);

    vll f(10,0);
    forn(0,9) f[a[i]-1]++;

    forn(0,10) if(!f[i]) cout<<i+1<<nl;
    return 0;
}