#include <iostream>
using namespace std;
typedef long long ll;

const ll MOD = 1000000007;

ll com[32][32];
ll dp[100005][32];

int main()
{
    int n;
    cin >> n;
    int b[100005];
    b[0] = 0;
    for(int i = 1; i <= n; i++) cin >> b[i];
    ll ans = 1;
    int l = 0;
    for(int i = 0; i < 30; i++){
        com[i][0] = 1;
        for(int j = 1; j <= i; j++) com[i][j] = (com[i - 1][j] + com[i - 1][j - 1]) % MOD;
    }
    for(int i = 1; i <= n; i++){
        if(b[i] == -1) continue;
        if((b[i] & b[l]) != b[l]){
            cout << 0 << endl;
            return 0;
        }
        int c = 0;
        int d = 0;
        int x = b[l] ^ b[i];
        for(int j = 0; j < 30; j++){
            c += (x >> j) & 1;
            d += (b[l] >> j) & 1;
        }
        for(int k = 0; k <= i - l; k++){
            for(int j = 0; j <= c; j++) dp[k][j] = 0;
        }
        dp[0][0] = 1;
        for(int k = 1; k <= i - l; k++){
            for(int j = 0; j <= c; j++){
                for(int m = 0; m < j; m++){
                    dp[k][j] = (dp[k][j] + dp[k - 1][m] * com[c - m][j - m] % MOD * (1 << (d + m))) % MOD;
                }
                dp[k][j] = (dp[k][j] + dp[k - 1][j] * ((1 << (d + j)) - 1)) % MOD;
            }
        }
        ans = ans * dp[i - l][c] % MOD;
        l = i;
    }
    cout << ans << endl;
}