         }
         let width:CGFloat = self.collectionView.frame.size.width - sectionInset.left-sectionInset.right
         let spaceColumCount:CGFloat = CGFloat(self.columnCount-1)
-        return floor(width - (spaceColumCount*self.minimumColumnSpacing) / CGFloat(self.columnCount))
+        return floor((width - (spaceColumCount*self.minimumColumnSpacing)) / CGFloat(self.columnCount))
     }
     
     override func prepareLayout(){

            
            let width = self.collectionView.frame.size.width - sectionInset.left - sectionInset.right
            let spaceColumCount = CGFloat(self.columnCount-1)
            let itemWidth = floor(width - (spaceColumCount*self.minimumColumnSpacing) / CGFloat(self.columnCount))
            
            /*
            * 2. Section header

}

class CHTCollectionViewWaterfallLayout : UICollectionViewLayout{
    let CHTCollectionElementKindSectionHeader = "CHTCollectionElementKindSectionHeader"
    let CHTCollectionElementKindSectionFooter = "CHTCollectionElementKindSectionFooter"
    
    var columnCount : NSInteger{
