N = int(input(""))
S = input("")
T = input("")

counter = 0
i = 0

def flip_number(S):
    S = S[::-1]

    return S

def change_number(S):
    S = list(S)
    if S[i] == "0":
        S[i] = "1"
    else:
        S[i] = "0"
    return S



    
for j in range(N):
    if S!= T:
        change_number(S)
        flip_number(S)
        counter += 1
        i += 1
    elif S == T:
        break

print(counter)