[백준][Python] 13305번 주유소

n = int(input())
length = list(map(int,input().split()))
price = list(map(int,input().split()))

min_value = price[0]
cost = 0
for i in range(len(length)):
    if price[i] < min_value:
        min_value = price[i]
    cost += min_value * length[i]
print(cost)