51nod 2635區間xor

求$a \oplus(a+1)\oplus\cdots\oplus(b-1)\oplus b$.

def f(n):
    m = n % 4
    if m==0:
        return n
    elif m==1:
        return 1
    elif m==2:
        return n+1
    else:
        return 0
if __name__ == '__main__':
    a, b = map(int, input().split())
    print(f(b) ^ f(a - 1))