Your company, established in 2001, is gradually moving its workloads from on-premises to Google Cloud Platform (GCP) VMs. A group of already migrated VMs operates in a subnet with a subnet mask of 255.255.255.220, which has exhausted its available IP addresses. You plan to migrate an additional 15 VMs to the same subnet, requiring seamless connectivity among all VMs without the need for extra routes. What is the best approach to achieve this?