#include <bits/stdc++.h>
#include <atcoder/modint>

using namespace std;
using namespace atcoder;

using mint = modint1000000007;

vector<mint> fact, inv;

void init(int n)
{
    fact.push_back(1);
    inv.push_back(1);
    for (int i = 0; i < n; i++)
    {
        fact.push_back(fact.back() * (i + 1));
        inv.push_back(1 / fact.back());
    }
}

mint ncr(int n, int r)
{
    if (r < 0 or n - r < 0)
    {
        return 0;
    }
    return fact[n] * inv[r] * inv[n - r];
}

mint calc(int n, int pc0, int pc)
{
    vector dp(n + 1, vector<mint>(pc - pc0 + 1));
    dp.at(0).at(0) = 1;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j <= pc - pc0; j++)
        {
            for (int k = 0; k <= pc - pc0; k++)
            {
                dp.at(i + 1).at(k) += dp.at(i).at(j) * ((1 << (pc0 + j)) * ncr(pc - pc0 - j, k - j) - (j == k));
            }
        }
    }
    return dp.at(n).at(pc - pc0);
}

int main(int argc, char const *argv[])
{
    int n;
    cin >> n;
    vector<int> b(n + 1);
    for (int i = 0; i < n; i++)
    {
        cin >> b.at(i + 1);
    }

    init(30);
    mint ans = 1;
    int last = 0;
    for (int i = 0; i < n; i++)
    {
        if (b.at(i + 1) != -1)
        {
            if ((b.at(last) & b.at(i + 1)) != b.at(last))
            {
                ans = 0;
                break;
            }
            ans *= calc(i + 1 - last, __builtin_popcount(b.at(last)), __builtin_popcount(b.at(i + 1)));
            last = i + 1;
        }
    }
    cout << ans.val() << endl;
    return 0;
}