#include <limits>
#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <map>
#include <queue>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using namespace std;

template<class T>
constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

int main() {
    string a,b,c;
    cin >> a >> b >> c;
    if(a == b) cout << a << "\n";
    else if(b == c) cout << b << "\n";
    else if(c == a) cout << c << "\n";
    return 0;
}