FOrmat sitemap module in two columns

I want to format my sitemap sub-menus list in two columns vertically how to do that? I have done it horizontally using width: 50% for sub-menus li tag.
Please check attached screenshot. Factsheet menu item is in second column, I want to fill first column & then second column. Means Factsheet should be below company profile.

Listing should be :
Left column:
Company Profile
Fact Sheet
Our People
Rengarajan S. Ragavan
Ralph W. Poole III
Charles Allman
Isabella D. Palowitch

Right column:
Our Partners
Autonomy
Coveo
SAP
Smartlogic
Our Expertise
Archiving
Business Intelligence
Business Process Management
Enterprise Capture and Imaging
Case Management
Collaboration
Community Management
Needs to divide menu items equally in two columns.