class NullError(Exception):
    def __init__(self,value):
        self.value = value
    def __str__(self):
        return repr(self.value)

class SomeDict(dict):
    def __init__(self,dic):
        self.gg=dic
    def __getitem__(self, key):
        v=self.gg[key]
        if v==-9999:
            raise NullError(key)
        return v
    def __len__(self):
        return len(self.gg)
    def __contains__(self, item):
        return item in self.gg
def TEval(ss,dic):
    try:
        return eval(ss,globals(),SomeDict(dic))
    except NullError:
        return -9999