def maximum(s):
    max = 0
    maxi = 0
    n=len(s)
    for i in range(n):
        if (str[i] == '('):
            max+=1;
            if(max>maxi):
                maxi=max
        elif (str[i] == ')'):
            if(max > 0):
                max-=1;
            else:
                return -1;
    if(max !=0):
        print("Not Valid")
        return -1;
    return maxi;
s=input("Enter a string")
print (maximum(s))