# 读取输入
n, m = map(int, input().split())  # 项目总数，小A参加的项目数
happiness = list(map(int, input().split()))  # 每个项目的欢乐度
attended_projects = list(map(int, input().split()))  # 小A参加的项目编号

# 计算小A的总欢乐度
total_happiness = sum(happiness[i - 1] for i in attended_projects)

# 输出结果
print(total_happiness)