#include <iostream>
#include <string>
#include <vector>
int main(void) {
  
  int32_t a, b, c;
  std::cin >> a >> b >> c;
  
  if (a == b && b == c) std::cout << a << std::endl;
  else if (a == b) std::cout << c << std::endl;
  else if (b == c) std::cout << a << std::endl;
  else if (c == a) std::cout << b << std::endl;
  else if (a != b && b != c && c != a) std::cout << 6 - (a+b+c) << std::endl;
  return 0;
}