#include "bits/stdc++.h"
#include "atcoder/all"
using namespace std;
using namespace atcoder;
using mint = modint1000000007;
const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"

struct combination {
	vector<mint> fact, ifact;
	combination(int n) :fact(n + 1), ifact(n + 1) {
		assert(n < mod);
		fact[0] = 1;
		for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
		ifact[n] = fact[n].inv();
		for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
	}
	mint operator()(int n, int k) {
		return com(n, k);
	}
	mint com(int n, int k) {
		if (n < 0) return com(-n, k) * (k % 2 ? -1 : 1);
		if (k < 0 || k > n) return 0;
		return fact[n] * ifact[k] * ifact[n - k];
	}
	mint inv(int n, int k) {
		if (n < 0) return inv(-n, k) * (k % 2 ? -1 : 1);
		if (k < 0 || k > n) return 0;
		return ifact[n] * fact[k] * fact[n - k];
	}
}c(200005);

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N;
	cin >> N;
	vector<int>B(N);
	rep(i, N) { cin >> B[i]; }
	vector<pair<int, int>>subB;
	subB.push_back({ 0,0 });
	rep(i, N) {
		if (-1 == B[i]) {
			continue;
		}
		subB.push_back({ B[i],i + 1 });
	}
	mint ans = 1;
	vector<mint>pow2(100005);
	rep(i, N + 1) {
		if (0 == i) {
			pow2[i] = 1;
		}
		else {
			pow2[i] = pow2[i - 1] * 2;
		}
	}
	rep(i, subB.size() - 1) {
		auto bef = subB[i];
		auto aft = subB[i + 1];
		mint anssub = 0;
		rep(j, aft.second - bef.second + 1) {
			//★★
			mint anssubsub = c(aft.second - bef.second, j);
			vector<int>pat(4, 0);
			rep(k, 30) {
				int x = 1 & (bef.first >> k);
				int y = 1 & (aft.first >> k);
				if ((1 == x) && (0 == y)) {
					pat[0]++;
				}
				else if ((0 == x) && (1 == y)) {
					pat[1]++;
				}
				else if ((0 == x) && (0 == y)) {
					pat[2]++;
				}
				else {//11
					pat[3]++;
				}
			}
			rep(k, 4) {
				rep(l, pat[k]) {
					if (0 == k) {
						anssubsub *= 0;
					}
					else if (1 == k) {
						anssubsub *= pow2[aft.second - bef.second - j] - 1;
					}
					else if (2 == k) {
						anssubsub *= 1;
					}
					else {
						anssubsub *= pow2[aft.second - bef.second - j];
					}
				}
			}
			if (0 == j % 2) {
				anssub += anssubsub;
			}
			else {
				anssub -= anssubsub;
			}
		}
		ans *= anssub;
	}
	cout << ans.val() << endl;
	return 0;
}