def shipTheseusParadox():
    N_Of_Planks = int(input())
    state = input()
    o_blueprint = input() 
    plank = 0
    if state == o_blueprint:
        return 0
    else:
        for i in range(N_Of_Planks):
            if state[i] != o_blueprint[i]:
                plank += 1
    print(plank)
shipTheseusParadox()