def my_xor(a, b):
    x = ""
    #my_xor("ab123a9c", "9a943a44")
    if len(a) >= len(b):
        for i in range(0,len(b)/2):
            print i
            #number = int(a[2*i:2], 16)
            print a[2*i:2]
            #print int(a[2*i:2],16)