#!/bin/python3

import itertools

MOD = 10 ** 9 + 7

'''
Sherlock's Array Merging Algorithm
@param V: array of vectors
@return M: Sherlock's result 
'''
def sherlock(V):
    M = []
    k = len(V)
    while (len(V) > 0):
        T = []
        i = 1
        while i <= k:
            if V[i] != []:
                el = V[i][0]
                V[i] = V[i][1:]
                T = [el] + T
            i += 1
        T = sorted(T)
        while T != []:
            el = T[0]
            T = T[1:]
            M = [el] + M
    return M

def solve(n, m):
    if m == sorted(m):
        return 2 ** (n - 1) % MOD
    return 1





n = int(input().strip())
m = list(map(int, input().strip().split(' ')))

print(str(solve(n, m)))