import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int p[] = new int[N + 1]; p new int[N + 1] N + 1 N 1 int miss = 0; miss 0 for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		} int i = 1; int i = 1; i 1 i <= N i N i++ i++ i {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		} {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		} p[i] = sc.nextInt() p[i] p i sc.nextInt() sc.nextInt sc if (p[i] != i) miss++; p[i] != i p[i] p i i miss++ miss if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		} miss == 2 || miss == 0 miss == 2 miss 2 miss == 0 miss 0 {
			System.out.println("YES");
		} System.out.println("YES") System.out.println System.out System System.out "YES" {
			System.out.println("NO");
		} System.out.println("NO") System.out.println System.out System System.out "NO" String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int p[] = new int[N + 1];
		int miss = 0;

		for (int i = 1; i <= N; i++) {
			p[i] = sc.nextInt();

			if (p[i] != i) miss++;
		}

		if (miss == 2 || miss == 0) {
			System.out.println("YES");
		} else {
			System.out.println("NO");
		}
	}
}
