import java.util.*;
import static java.lang.System.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] p = new int[n];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			out.println("NO");
	}
} import java.util.*; util.* java import static java.lang.System.*; import static java.lang.System.*; import static java.lang.System.*; public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] p = new int[n];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			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];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			out.println("NO");
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] p = new int[n];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			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]; p new int[n] n int[] q = new int[n]; q new int[n] n int cnt = 0; cnt 0 for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		} {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		} p[i] = sc.nextInt() p[i] p i sc.nextInt() sc.nextInt sc q[i] = i + 1 q[i] q i i + 1 i 1 for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			if (p[i] != q[i])
				cnt++;
		} {
			if (p[i] != q[i])
				cnt++;
		} if (p[i] != q[i])
				cnt++; p[i] != q[i] p[i] p i q[i] q i cnt++ cnt if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			out.println("NO"); cnt == 0 || cnt == 2 cnt == 0 cnt 0 cnt == 2 cnt 2 out.println("YES") out.println out "YES" out.println("NO") out.println 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];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			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];
		int[] q = new int[n];
		int cnt = 0;
		for(int i = 0; i < n; i++) {
			p[i] = sc.nextInt();
			q[i] = i + 1;
		}
		for(int i = 0; i < n; i++) {
			if (p[i] != q[i])
				cnt++;
		}
		if (cnt == 0 || cnt == 2)
			out.println("YES");
		else
			out.println("NO");
	}
} Main
import java.util.*;
import static java.lang.System.*;

public class Main {

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