if you have access to a linux box, it's easy, here's a bash script that does what I mentioned above and creating the .rsc script to import them in RouterOS:
#!/bin/bash
#Replace file.ips with the name of the file with your original range ips
ORGFILE="file.ips"
#empty the files :-)
echo > file.tmp
echo "/ip firewall address-list" > script.rsc
echo ":foreach subnet in [/ip firewall address-list find list=Country] do {" >> script.rsc
echo "/ip firewall adress-list remove $subnet" >> script.rsc
echo "}" >> script.rsc
echo "###" >> script.rsc
for range in $(cat file.ips); do
ipcalc $range | grep -v deaggregate;
done >> file.tmp
for cidr in $(cat file.tmp); do
echo "add list=Country address=$cidr disabled=no";
done >> script.rsc
Create a the file, copy/paste there and chmod +x file, then just run the file with ./file
Remember to change the name of the file that contains your original IPs, and make sure it's in the same directory as the script.
After that, just upload the script.rsc file to your mikrotik routeros and do /import script.rsc
If you need more assistance, just ask.