import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int b = 0;
        for(int i = 0; i<=8; i++){
            int a = sc.nextInt();
            b +=1;
            if(a!=b){
            	System.out.println(b);
            	break;
            }
        }
        System.out.println(10);
    }
}