getting a substring

coding i have done so far but not working

 

using System;

namespace HelloWorld
{
class Program
{
static void Main(string[] args)
{
string lyric = "Just a small town girl";
string firstFourCharacters, lastFourCharacters;

firstFourCharacters = lyric.IndexOf"just";

lastFourCharacters = lyric.Indexof"girl";

Console.WriteLine(firstFourCharacters + " " + lastFourCharacters);
}
}
}