题解 | #矩阵乘法计算量估算#

while True:
    try:
        n = int(input())
        L = []
        stack = []
        for i in range(n):
            L.append(tuple(map(int, input().split())))
        M = input()
        i = 0
        num = 0
        for m in M:
            if m.isalpha():
                stack.append(L[i])
                i += 1
            elif m == ")":
                b = stack.pop()
                a = stack.pop()
                num += a[0] * b[0] * b[1]
                stack.append((a[0], b[1]))
        print(num)
    except:
        break