题解 | #矩阵乘法计算量估算#

n = int(input())
ls = []
for i in range(n):
    ls.append(list(map(int,input().split())))
s = input() # (A(BC))
stack = []
cc = 0
for i in s:
    if i.isalpha():
        stack.append(ls[ord(i)-65])
    elif i == ')' and len(stack) >= 2:
        a = stack.pop()
        b = stack.pop()
        cc += a[0]*a[1]*b[0]
        stack.append([b[0],a[1]])
print(cc)