题解 | #矩阵乘法计算量估算#

'''


3
50 10
10 20
20 5
(A(BC))
'''
# 3500

n = int(input())        # 矩阵个数n
ls = []
guize = []
cc = 0
for i in range(n):
    ls.append(list(map(int,input().split())))

s = input()  # 计算规则：  (A(BC))
for i in s:
    if i.isalpha():
        guize.append(ls[ord(i)-65])# 将字母转换成第几个矩阵的处理信息
    elif i == ')' and len(guize) >= 2:
        c = guize.pop()     #先弹出的是后输入的
        b = guize.pop()
        cc += b[0]*c[1]*b[1]
        guize.append([b[0],c[1]])
print(cc)