import java.util.*;

public class No365{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		ArrayList<Integer> a = new ArrayList<Integer>();
		for(int i = 0; i < n; i++){
			a.add(sc.nextInt());
		}
		int count = 0;
		int idx = 0;
		for(int i = 0; i < n; i++){
			if(a.get(idx) != i+1){
				a.remove(a.indexOf(i+1));
				count++;
			}else{
				idx++;
			}
		}
		System.out.println(count);
	}
}