#include<iostream>
#include<algorithm>
#include<atcoder/modint>
using namespace std;
using mint=atcoder::modint1000000007;
int N;
int A[2<<17];
main()
{
	cin>>N;
	for(int i=0;i<N;i++)cin>>A[i];
	mint X=0,Y=A[0];
	for(int i=1;i<N;i++)
	{
		X=X*3+2*Y;
		Y*=A[i];
	}
	cout<<(X+Y).val()<<endl;
}