#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
#include <queue>
#include <map>
#include <cmath>
#include <iomanip>
#include <set>
#include <cstdio>
#include <string>

using namespace std;

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