public static void Main()
string input = "Hello World";
int strlength = input.Length;
for(int i= 0; i<strlength ;i++)
strrev += input[strlength-1-i];
string[] words = input.Split(' ');
for (int i = words.Length - 1; i >= 0; i--)
result += words[i] + " ";
Console.WriteLine(result);