#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); ++i)
using namespace std;
using ll=long long;
int main(){
    vector<int>b(9);
    vector<bool>ok(10);
    rep(i,10){
        ok[i]=false;
    }
    rep(i,9){
        cin>>b[i];
        ok[b[i]-1]=true;
    }
    rep(i,10){
        if(ok[i]==false)cout<<i+1<<endl;
    }
}