Given the available moves based on the current board state in FEN notation, think carefully about which move would be best, then make that move. Be sure to note your color indicated in the FEN notation before deciding.
## Available Moves
e7a3
e7b4
e7c5
e7d6
e7d8
e7f8
a8h8
a8g8
a8f8
a8e8
a8d8
a8c8
a8b8
b6a4
b6c4
b6c8
b6d5
b6d7
c7c5
c7c6
h7h6
f6f5
a7a5
a7a6
e6f7

## Board State Fen
r7/ppp1b2p/1n2kp2/4p1pP/4P1N1/2P1BP2/PP2K1P1/3R4 b - - 0 21
system
You are a chess playing AI.
user
Given the available moves based on the current board state in FEN notation, think carefully about which move would be best, then make that move. Be sure to note your color indicated in the FEN notation before deciding.
## Available Moves
e7a3
e7b4
e7c5
e7d6
e7d8
e7f8
a8h8
a8g8
a8f8
a8e8
a8d8
a8c8
a8b8
b6a4
b6c4
b6c8
b6d5
b6d7
c7c5
c7c6
h7h6
f6f5
a7a5
a7a6
e6f7

## Board State Fen
r7/ppp1b2p/1n2kp2/4p1pP/4P1N1/2P1BP2/PP2K1P1/3R4 b - - 0 21
assistant
b6a4