gistfile1.txt

dim = [19, 119]; // exemplo

var group, lastgroupsize;
  		
			_.each(dim, function(item, index) {
				
				if(index == 0) {
					lastgroupsize = item;
					if(i < item) {
						group = index;
					}
				} else {
					if(i >= lastgroupsize && i < item) {
						group = index;
					}
				}
				
});