题解 | #矩阵乘法计算量估算#

n = int(input())
arr = []
for i in range(n):
    tmp = list(map(int, input().strip().split()))
    arr.append(tmp)
strings = input().strip()

tmp_arr = []
res = 0
for i in strings:
    if i.isalpha():
        a = ord(i) - 65
        tmp_arr.append(arr[a])
    elif i == ')' and len(tmp_arr) >= 2:
        n2 = tmp_arr.pop()
        n1 = tmp_arr.pop()
        res += n1[0] * n1[1] * n2[1]
        tmp_arr.append([n1[0], n2[1]])

print(res)