import java.util.Scanner;

public class four_fruits {
  public static void main(String[] args) {
    boolean[] bools = { false, false, false, false };
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int c = sc.nextInt();
    sc.close();
    bools[a] = true;
    bools[b] = true;
    bools[c] = true;
    int cnt = 0;
    for (boolean i : bools) {
      if (i) {
        cnt++;
      }
    }
    int out = 0;
    switch (cnt) {
      case 1:
        out = a;
        break;
      case 2:
        if (a == b) {
          out = c;
        } else if (b == c) {
          out = a;
        } else {
          out = b;
        }
        break;
      case 3:
        for (int i = 0; i < 3; i++) {
          if (bools[i] == false) {
            out = i;
          }
        }
    }
    System.out.println(out);
  }
}