15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, xx, xx, xx, xx, 63
xx, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, xx, xx, xx, xx, xx
URL Safe Base64 in Objective-C