Ab13

 ======
 ||||||
 ------
 |||||1  2nd fret
 ------
 |222||
 ------
 3|||4|
 ------
 ||||||
 ------
 ACFBEG
 b  bbb

or:

 ======
 ~~~~~~
 ------
 1-1--1  4th fret
 ------
 |||2||
 ------
 |3||4|
 ------
 ||||||
 ------
 AEGCFA
 bbb  b

or:

 ======
 ~~~~~~
 ------
 1-1|||  4th fret
 ------
 |||2||
 ------
 |3||44
 ------
 ||||||
 ------
 AEGCFB
 bbb  b

Notes:  1  : Ab
        3  : C
        5  : Eb
        b7 : Gb
        9  : Bb
        13 : F