import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int rest01 = sc.nextInt();
        int rest02 = sc.nextInt();

        int res = 0;
        int cnt = 1;
        while (cnt <= sc.nextInt()) {
            if (cnt != rest01 && cnt != rest02) {
                res++;
            }
            cnt++;
        }
        System.out.print(res);
    }
}