@staticmethod
def b():
    (s, t) = sys.stdin.read().split()
    print(sum(((s[i] != t[i]) for i in range(len(s)))))
@staticmethod
def b():
    (s, t) = sys.stdin.read().split()
    print(sum(((s[i] != t[i]) for i in range(len(s)))))