题解 | #矩阵乘法计算量估算#

def jc(x,y):
    return ((x[0],y[1]),x[0]*x[1]*y[1])
n=int(input())
ls=[]
for i in range(n):
    ls.append(tuple(map(lambda x:int(x),input().split(" "))))
rule=input()

ls2=[x if x in ("(",")") else ls[ord(x)-ord("A")] for x in rule]
count=0
while True:
    if len(ls2)<=1:
        break
    start=0
    for i in range(len(ls2)):
        if ls2[i]=="(":
            start=i
        elif ls2[i]==")":
            if((i-start)==2):
                x=ls2[start+1]
            else:
                x=ls2[start+1]
                for j in range(start+2,i):
                    result=jc(x,ls2[j])
                    x=result[0]
                    count+=result[1]
            ls2 = ls2[:start]+ls2[i+1:]
            ls2.insert(start,x)
            break

print(count)