BOJ 14991 - Disastrous Doubling [Python]

문제

링크

풀이

n = int(input())
b = list(map(int, input().split()))
 
ans = 1
for i in range(n):
  ans = 2 * ans - b[i]
  if ans < 0:
    print("error")
    exit()
 
mod = 1000000007
print(ans % mod)