#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int n, ans[1300], x[1301];
bool ok;

int main() {
    cin >> n;
    ans[0] = 1;
    for (int i = 1; i <= n; ++i)
    {
        cin >> x[i];
        if (x[i] < x[i - 1]) ok = true;
        ans[i] =  (ans[i - 1] * 2) % 1000000007;
    }
    if (ok) cout << 1;
    else
    cout << ans[n - 1];
    
    return 0;
}