#include <iostream>
#include <vector>
#include <queue>
#include <cassert>
#include <algorithm>

using namespace std;
// using namespace atcoder;

typedef long long ll;
typedef long double ld;

const ll INF = 1LL << 60;
const ll MOD = 998244353;
// using mint = modint998244353;
const string NEW_LINE = "\n";

inline void output_YesNo(bool x) { cout << (x ? "Yes" : "No") << endl; }
template<typename T>
inline void chmax(T &lhs, const T &rhs) { lhs = max(lhs, rhs); }
template<typename T>
inline void chmin(T &lhs, const T &rhs) { lhs = min(lhs, rhs); }

// #include <iomanip>
//
// void init_output() { cout << fixed << setprecision(15); }

int main() {
    int a, b, c;
    cin >> a >> b >> c;
    cout << (a ^ b ^ c) << endl;
    return 0;
}