题解 | #矩阵乘法计算量估算#

# 2024年9月23日
n = int(input())
ls = []
stack = []
for i in range(n):
   ls.append(list(map(int,input().split())))
#print(ls)
f = input() # (A(BC))
cc = 0
for i in f:
    if i.isalpha():
        stack.append(ls[ord(i)-65])
    elif i == ')' and len(stack) >= 2:
        c = stack.pop()
        b = stack.pop()
        cc += c[0]*c[1]*b[0]
        stack.append([b[0],c[1]])
print(cc)