import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

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

        int i = 1;

        for(i=1; i<11; i++) {
            int x = in.nextInt();
            if(x != i) break;
        }

        System.out.println(i);

        in.close();
    }
}