题解 | #矩阵乘法计算量估算#

num=int(input())
list1=[]
for i in range(num):
    tup1=tuple(map(int,input().split(' ')))
    list1.append(tup1)
order=input()

def trans(str1):
    tnum=ord(str1)-ord('A')
    return (tnum)

def mult(tup1,tup2):
    num=tup1[0]*tup1[1]*tup2[1]
    new_tup=(tup1[0],tup2[1])
    return(new_tup,num)

tmp=[]
count=0
for i in order:
    if i!='(' and i!=')':
        tmp.append(list1[trans(i)])
        #入栈
    if i==')':
        new_tup,num=mult(tmp[-2],tmp[-1])
        count+=num
        if len(tmp)>2:
            tmp=tmp[0:-2]
        elif len(tmp)==2:
            tmp=[]
        tmp.append(new_tup)
        #出栈
print(count)