My C# solution

public static void Main(string[] args) { int n = Convert.ToInt32(Console.ReadLine().Trim());

    string binary = Convert.ToString(n ,2);

    char[] c = binary.ToCharArray();

    int iCount = 1;   
    int left = 0;
    int right = 1;
    // This list will be used to store each count.
    // After each iteration, we add the count to the list.
    // After the loop has finished, we sort the elements in the 
    //list,
    // and finally, we print the last element of the list.
   List<int> lstCounts = new List<int>();

    for(int i = 0 ; i < c.Length ; i++)
    {
         if(right <= c.Length -1 )
        {
             if(c[left] == c[right] && c[right] == '1')
            { 
                iCount++;
                lstCounts.Add(iCount);
            }
             else 
             { 
                lstCounts.Add(iCount);
                iCount = 1;
             }
        }

        left++;
        right++;          
    }

// sort elements from the list  
 lstCounts.Sort();
 //print the highest count from the list
 Console.Write(lstCounts.LastOrDefault()); 


}