#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
using namespace std;


int main()
{
    long long n, a ,b ,c;
    string s;
    vector<long long> v(3);
    set<long long> add;
    cin >> n >> v[0];

    getline(cin, s);
    if (s.size()){
        cout << "\"assert\"" << endl;
        return 0;
    }
    for (int i = 1; i < 3; i++) cin >> v[i];
    add.insert(v[0] + v[1]);
    add.insert(v[1] + v[2]);
    add.insert(v[0] + v[2]);
    auto itr = add.begin();
    if (add.size()==3){
        itr++;
        cout << *itr << endl;
    }
    else if (add.size() == 2) cout << *itr << endl;
}