I provided the value to the variable as shown below and executed the job.
The job failed with below error
Executed as user: Domain\svsSSISAccount. Microsoft (R) SQL Server Execute Package Utility Version 10.50.2500.0 for 32-bit Copyright (C) Microsoft Corporation 2010. All rights reserved. The argument "\Package.Variables[User::FolderPath].Value;\\ServerName\MainFolder\InputFiles" /REPORTING E " has mismatched quotes. The command line parameters are invalid. The step failed.
Adding "\" did the trick so the value of variable looks like \\ServerName\\MainFolder\\InputFiles