#include <iostream>
#include <vector>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
namespace mp = boost::multiprecision;
int main() {
    vector<mp::cpp_int> v;
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        int a;
        cin >> a;
        v.push_back(a);
    }
    
    while (v.size() > 1) {
        vector<mp::cpp_int> tmp;    
        for (size_t i = 0; i < v.size(); ++i) {
            if (i + 1 < v.size()) {
                tmp.push_back(v[i] + v[i + 1]);
            }
        }
        v = tmp;
    }

    unsigned long long m = 1000000007LL;
    cout << v[0] % m << endl;
    
    return 0;
}