PATH=/bin:/usr/bin

low=0
high=101

while test $low -lt `expr $high - 1`
do
    guess=`expr $low + $high`
    guess=`expr $guess / 2`
    echo "Is your number >=$guess or <$guess?  Enter 'g' or 'l'."
    read input
    case "$input" in
	l)
	    high=$guess
	    ;;
	g)
	    low=$guess
	    ;;
    esac
done
echo Your number must be $low.