Bourne shell: ignoring certain kinds of stdin

I have a program that is currently working, but I need to modify it to ignore some stdin that is not fitting for its correct function.

Right now, to run the program: printf "1\n3\n5\n" | sh prog

The program currently ignores non-integer input (like floats), but I also need it to ignore something like '4 10' on the same line and '5 text' etc.

#! /bin/sh

sum=0;  
cnt=0

while read line
do

   case "$line" in

        *[.]*  )   #------I think here is where the regex needs to be edited
            printf "\n0"
            continue
            ;;

        [0-9]* )
            sum=`expr "$sum" + "$line"`
           cnt=`expr "$cnt" + 1`
            printf "\n%s" `expr $sum / $cnt`
            ;;
    esac

done

I'm pretty sure it's just a matter of changing the regex on the line I pointed out so that it goes to the print 0 and continue case with the two non-desired input types I described above but I am having trouble with it.

Thank you!