z = int(input())

l = input()

def r(i):
    res = 0
    while i < len(l) and l[i] != ')':
        mul, i = r(i+1)
        if res == 0:
            res = mul
        else:
            res *= mul
    return (res + 1, i + 1)
    
    
res, _ = r(0)
print(res - 1)