#include<bits/stdc++.h>
// #include<atcoder/all>
// #include<boost/multiprecision/cpp_int.hpp>

using namespace std;
// using namespace atcoder;
// using bint = boost::multiprecision::cpp_int;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007


// 2020/12/06 rechecked
class Comb{
  public:
  const int n;
  const int mod = 1000000007;
  // const int mod = 998244353;
  vector<long long> fac,refac;
  Comb(int N) : n(N),fac(N+1,1),refac(N+1,1) {
    for(int i = 0;i < n;i++)fac[i+1] = fac[i]*(i+1)%mod;
    refac[n] = modpow(fac[n],mod-2);
    for(int i = n;i > 0;i--)refac[i-1] = refac[i]*i%mod;
  }
  long long comb(long long n,long long r){
    if(n < r)return 0;
    long long res = fac[n]*refac[r]%mod;
    res = res*refac[n-r]%mod;
    return res;
  }
  long long modpow(long long n,long long r){
    long long res = 1;
    while(r){
      if(r & 1)res = res*n%mod;
      n = n*n%mod;
      r >>= 1;
    }
    return res;
  }
};

int main(){
  
  int n;
  cin >> n;
  vector<int> b(n);
  rep(i,n)cin >> b[i];
  {
    int pre = 0;
    rep(i,n){
      if(b[i] == -1)continue;
      if((b[i] & pre) != pre){
        cout << 0 << "\n";
        return 0;
      }else pre = b[i] | pre;
    }
  }
  int x = 0;
  int cnt = 0;
  ll res = 1;
  Comb cb(100);
  vector<ll> two(100,1);
  rep(i,99)two[i+1] = two[i]*2%MOD;
  rep(i,n){
    if(b[i] == -1)cnt++;
    else {
      int nx = __builtin_popcount(b[i]);
      cnt++;
      vector<ll> dp(nx-x+1);
      dp[0] = 1;
      rep(j,cnt){
        vector<ll> DP(nx-x+1);
        rep(k,nx-x+1)rep(l,k+1){
          if(k != l)DP[k] = (DP[k] + (dp[l]*two[x+l]%MOD)*cb.comb(nx-x-l,k-l)%MOD)%MOD;
          else DP[k] = (DP[k] + (dp[l]*(two[x+l]-1+MOD)%MOD))%MOD;
        }
        swap(dp,DP);
      }
      (res *= dp[nx-x])%= MOD;
      cnt = 0;
      x = nx;
    }
  }
  cout << res << "\n";
  

  return 0;
}