#include <bits/stdc++.h>


using namespace std;
typedef long long ll;
#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define VB vector<bool>
#define VVB vector<vector<bool>>
#define fore(i,a) for(auto &i:a)

typedef pair <int, int> P;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
const int  INF = 1 << 30;
const ll INFL = 1LL << 60;
const ll mod = 998244353;


int main() {
	
	string n;
	getline(cin, n);
	string s;
	getline(cin, s);
	if (s.size() != 1) {
		cout << '"' << "assert" << '"' << endl;
		return 0;
	}
	int a = s[0] - '0';
	int b, c;
	cin >> b >> c;
	VI d;

	d.push_back(a + b);
	d.push_back(a + c);
	d.push_back(b + c);

	sort(ALL(d));
	if (d[1] == d[2])cout << d[0] << endl;
	else cout << d[1] << endl;


	
}