Problem in uploading the program

I got new Arduino Uno r3.

Installed Arduino IDE 1.6.5

Installed the required drivers

( It assigned port18 )

Opened Arduino IDE
Selected Arduino Uno/Genuino under boards
Selected com18 under ports

Tried to upload blink example

On first the go of upload, it became idle
On the second go. It showed following error

avrdude: ser_open(): can't open device "\.\COM18": Access is denied.

Please provide me solution