using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(replaceSpace(new char[]{'t',' ','e',' ','s','t',' ',' ',' ',' '},6));

    }

    public static string replaceSpace(char[] str, int trueLength){

        int ptr1 = str.Length-1;

        int ptr2 = trueLength - 1;

        while(ptr2 > 0){

            if(str[ptr2] != ' '){

                str[ptr1--] = str[ptr2--];

            }else{

                str[ptr1--] = '0';

                str[ptr1--] = '2';

                str[ptr1--] = '%';

                ptr2--;

            }

        }

        return new string(str);

    }

}