import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int [] a = new int [N];
        int [] b = new int [N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        int r=N;
        int t=N-1;
        for(int i=t; i>=0; i--){
            if(a[i]==r){
                r--;
                t--;
                continue;
            }
        }
        System.out.println(r);
    }
}