#include "bits/stdc++.h"
#define in std::cin
#define out std::cout
#define rep(i,N) for(LL i=0;i<N;++i)
typedef long long int LL;

const LL mod = 1000000007;

int main()
{
	LL N;
	in >> N;
	std::vector<LL>a(N);
	rep(i, N) in >> a[i];

	LL ans = 0;
	std::vector<LL>res;
	res.push_back(1);
	rep(i, N - 1)
	{
		std::vector<LL>res_new;
		res_new.resize(i + 2);
		res_new[0] = res_new[i + 1] = 1;
		for (int j = 1; j < i + 1; ++j) res_new[j] = (res[j - 1] + res[j]) % mod;
		res = res_new;
	}
	rep(i, N)
	{
		LL temp = ((a[i] % mod)*(res[i] % mod)) % mod;
		(ans += temp) %= mod;
	}

	out << ans << std::endl;
}