import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.stream.Stream;

public class Monsters {

    public static void main_1(String... args) throws Exception {
         // try (BufferedReader reader = new BufferedReader(new FileReader(new File("t8.in")))) {
         try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {

            String line;
            while ((line = reader.readLine()) != null) {
                int len = Integer.parseInt(line);

                int array[] = Stream.of(reader.readLine().split(" "))
                        .mapToInt(s -> Integer.parseInt(s)).toArray();

                int count = 0;
                for (int i = 0; i < array.length - 1; i++) {
                    int expected = i + 1;

                    int a = array[i];
                    int b = -1;

                    if (a != expected) {
                        for (int j = i + 1; j < array.length; j++) {
                            b = array[j];
                            if (b == expected) {
                                // swap
                                array[i] = b;
                                array[j] = a;
                                break;
                            }
                        }

                        count++;
                    }
                }

                System.out.println(count);
            }
        }
    }

    public static void main(String... args) throws Exception {
        //try (BufferedReader reader = new BufferedReader(new FileReader(new File("t8.in")))) {
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {

            String line;
            while ((line = reader.readLine()) != null) {
                int len = Integer.parseInt(line);
                int array[] = new int[len];

                StringTokenizer tokenizer = new StringTokenizer(reader.readLine(), " ");
                for (int i = 0; i < len; i++) {
                    String token = tokenizer.nextToken();
                    array[i] = Integer.parseInt(token);
                }

                int count = 0;
                for (int i = 0; i < array.length - 1; i++) {
                    int expected = i + 1;

                    int a = array[i];
                    int b = -1;

                    if (a != expected) {
                        for (int j = i + 1; j < array.length; j++) {
                            b = array[j];
                            if (b == expected) {
                                // swap
                                array[i] = b;
                                array[j] = a;
                                break;
                            }
                        }

                        count++;
                    }
                }

                System.out.println(count);
            }
        }
    }

}