/* -*- coding: utf-8 -*-
 *
 * 1934.cc:  No.1934 Four Fruits - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

int as[3], cs[4];

/* subroutines */

/* main */

int main() {
  for (int i = 0; i < 3; i++) scanf("%d", as + i);
  sort(as, as + 3);

  int x;
  if (as[0] == as[2]) x = as[0];
  else if (as[0] == as[1]) x = as[2];
  else if (as[1] == as[2]) x = as[0];
  else {
    for (int i = 0; i < 3; i++) cs[as[i]] = 1;
    for (int i = 0; i < 4; i++)
      if (cs[i] == 0) { x = i; break; }
  }

  printf("%d\n", x);
  return 0;
}