#!/bin/python3

import sys


n = int(input().strip())
m = list(map(int, input().strip().split(' ')))
# your code goes here
a=False
for i in range(len(m)-1):
    if m[i]<m[i+1]:
        a=True
    else:
        a=False
        break
if a == True:
    print((2**n)-n-1)
else:
    c=1
    for i in range(len(m)-1):
        if m[i]<=m[i+1]:
            c+=1
        else:
            break
    print (c)