#include <iostream>
#include <vector>
using namespace std;
int main() {
    vector<long long> 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<long long> tmp;    
        for (size_t i = 0; i < v.size(); ++i) {
            if (i + 1 < v.size()) {
                tmp.push_back((v[i] + v[i + 1]) % 1000000007LL);
            }
        }
        v = tmp;
    }
    cout << v[0] << endl;
    
    return 0;
}