class Problem0224:
    def solve(this):
        n = int(input())
        s = input()
        t = input()

        res = 0
        for i in range(0, len(s)):
            if s[i] != t[i]:
                res += 1
        print(res)

if __name__ == "__main__":
    problem = Problem0224()
    problem.solve()