Pizzeria

import sys
import math
import itertools
from collections import defaultdict

n = int(sys.stdin.readline().rstrip())

taytteet = map(int, sys.stdin.readline().rstrip().split())

pizzas = 1
money = taytteet[0]

for i in xrange(1, len(taytteet)):
	#print money
	money += (pizzas+1)*taytteet[i] + money
	pizzas = pizzas*2 + 1
	money = money % (10**9 + 7)


print money

# actually it just needs the number of pizzas previously
# new money to add when new filling comes:
# number of prev pizzas * new filing price + new filling price
# new number of pizzas:
# number of prev pizzas * 2 + 1

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 15

Group: 3

Verdict: TIME LIMIT EXCEEDED