using System;

public class Test
{
    public static void Main()
    {
        Console.WriteLine(ConvertToRanges("1,2,3,4,8,9,10,15"));
    	Console.WriteLine(ConvertToRanges("5,6,7,9,10,11,12,15,16"));
    }
    	
    public static string ConvertToRanges(string pageNos)
    {
    	string result=string.Empty;
    	string[] arr1 = pageNos.Split(',');
    	int[] arr = new int[arr1.Length];
    	
    	for (int x = 0; x < arr1.Length; x++) // Convert string array to integer array
    	{
    		arr[x] = Convert.ToInt32(arr1[x].ToString());
    	}
    	
    	int start,end;  // track start and end
    	end = start = arr[0];
    	for (int i = 1; i < arr.Length; i++)
    	{
    		// as long as entries are consecutive, move end forward
    		if (arr[i] == (arr[i - 1] + 1))
    		{
    			end = arr[i];
    		}
    		else
    		{
    			// when no longer consecutive, add group to result
    			// depending on whether start=end (single item) or not
    			if (start == end)
    				result += start + ",";
    			else
    				result += start + "-" + end + ",";
    	
    			start = end = arr[i];
    		}
    	}
    	
    	// handle the final group
    	if (start == end)
    		result += start;
    	else
    		result += start + "-" + end;
    	
    	return result;
    }
}