lel

def fbf(str):
    resp = True
    n = 0
    for x in str:
        if x==")":
            if n == 0: resp = False
            n-=1
        elif x=="(":
            n+=1
    if n!=0: resp = False
    return resp

noVale = ")("
print fbf(noVale)
vale = "(a^2) + b^2"
print fbf(vale)