import 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];
        for(int i = 0 ; i < n ; i++ ){
            p[i] = sc.nextInt();
            if(p[i] - 1 != i){
                p[i] = -1;
            }
        }
        if(n < 3){
            System.out.println("YES");
        }else{
            Arrays.sort(p);
            if(p[2] == -1){
                System.out.println("NO");
            }else{
                System.out.println("YES");
            }
        }
        sc.close();

    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz