How to extract the 15 digit IMEI from 21 digit IMEISV?

Redmi3s Imei Vs :unknown Slot1 - imei sv slot 1 slot1 or in both slots or no SIM card at all then IMEI for slot 1 will be used We will need to get rid of IMEI however due to Google policy imei slot 1 slot1 or in both slots or no SIM card at all then IMEI for slot 1 will be used We will need to get rid of IMEI however due to Google policy

imei sv slot 1 slot for such While it's not available worldwide and can often ; 下载2ndLine