how to upgrade server 2012 to server 2012 R2 without formating

[Shelax]

hi,

please reply to my question asap

how to upgrade server 2012 to server 2012 R2 without formating?

i have installed server 2012 standard evaluation version & purchased license copy of server r2 with 10 cal's

formatting will be headache because lots of softwares installed like personal & sql & sap.

please it's urgent.

thanks in advance