Grafana - ElasticSearch DataSource - Combing two values in a Pie Chart


I am using ElasticSearch as a Data Source for Grafana.

I am getting the below details for a Pie Chart

Here I want to Combine JAPAN and JAPAN-APAC and show it as a single value (JAPAN).
So basically it should hold the sum of both JAPAN and JAPAN-APAC.

Is there any way to achieve this. Please help.