题解 | #矩阵乘法计算量估算#
矩阵乘法计算量估算
http://www.nowcoder.com/practice/15e41630514445719a942e004edc0a5b
n = int(input())
dic= {}
for i in range(n):
dic[chr(ord('A')+i)] = list(map(int, input().split()))
al = input()
zimu = []
res = 0
ex = 0
for i in al:
if i.isalpha():
zimu.append(i)
elif i == ')':
b = zimu.pop()
a = zimu.pop()
res = res + dic[a][0]*(dic[b][0]*dic[b][1])
dic[ex] = [dic[a][0],dic[b][1]]
zimu.append(ex)
ex += 1
# (A((B(C(DE)))(FG)))
print(res)