0 0 -> 0 0
-1 ffffffffffffffff -> 1 1
1 1 -> 2 2
-63 ffffffffffffffc1 -> 125 7d
-64 ffffffffffffffc0 -> 127 7f
63 3f -> 126 7e
64 40 -> 128 80
-9223372036854775807 8000000000000001 -> 18446744073709551613 fffffffffffffffd
-9223372036854775808 8000000000000000 -> 18446744073709551615 ffffffffffffffff
9223372036854775806 7ffffffffffffffe -> 18446744073709551612 fffffffffffffffc
9223372036854775807 7fffffffffffffff -> 18446744073709551614 fffffffffffffffe