code: func symMerge(u Comparators, start1, start2, last int) {
  	if start1 < start2 && start2 < last {
  		mid := (start1 + last) / 2
  		n := mid + start2
  		var start int
  		if start2 > mid {
  			start = symBinarySearch(u, n-last, mid, n-1)
  		} else {
  			start = symBinarySearch(u, start1, start2, n-1)
  		}
  		end := n - start
  
  		symRotate(u, start, start2, end)
  		symMerge(u, start1, start, mid)
  		symMerge(u, mid, end, last)
  	}
  }
docs: // symMerge is the recursive and internal form of SymMerge.