#!/bin/python

from __future__ import print_function

import os
import sys
def canModify(a):

    count = 0
    for i in range(1,len(a)):
        if(a[i-1]>a[i]):
            count += 1
    if(count>1):
    return 'NO'
    else:
    return 'YES'

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    n = int(raw_input())

    a = map(int, raw_input().rstrip().split())

    result = canModify(a)

    fptr.write(result + '\n')

    fptr.close()