import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		sc.close();

		int mod = 1000000007;
		long[] p3 = new long[n];
		p3[0] = 1;
		for (int i = 1; i < n; i++) {
			p3[i] = p3[i - 1] * 3;
			p3[i] %= mod;
		}

		long ans = 0;
		long b = 1;
		for (int i = 0; i < n - 1; i++) {
			b *= a[i];
			b %= mod;
			long val = b * p3[n - 2 - i] * 2 % mod;
			ans += val;
		}
		b *= a[n - 1];
		b %= mod;
		ans += b;
		ans %= mod;
		System.out.println(ans);
	}
}