Shell Programming and Scripting

#!/bin/bash
read -p "amino acid: " AAA
if [ "$AAA" == "ALA" ] || [ "$AAA" == "VAL" ] || [ "$AAA" == "ARG" ] || [ "$AAA" == "ASN" ] || [ "$AAA" == "ASP" ] || 
   [ "$AAA" == "CYS" ] || [ "$AAA" == "GLY" ] || [ "$AAA" == "ILE" ] || [ "$AAA" == "LEU" ] || [ "$AAA" == "LYS" ] ||
   [ "$AAA" == "MET" ] || [ "$AAA" == "PHE" ] || [ "$AAA" == "PRO" ] || [ "$AAA" == "SER" ] || [ "$AAA" == "THR" ] || 
   [ "$AAA" == "TRP" ] || [ "$AAA" == "TYR" ] || [ "$AAA" == "HIS" ] || [ "$AAA" == "GLN" ] || [ "$AAA" == "GLU" ]
then 
	for i in HS_*.pdb.txt; do
			cat $i | grep -o -i $AAA | wc -l
    	done
elif [ "$AAA" == 0 ]
	then
		exit 1
else
	read -p "amino acid: " AAA
fi