using System;
using System.Linq;
 
public class Test
{
 
static double IntersectionSize(string a, string b) {
    var wordsA = a.Split(null);
    var wordsB = b.Split(null);
    var common = wordsA.Intersect(wordsB);
    double res = common.Sum(w => w.Length); // Total length of common words
    return 2 * res / (wordsA.Distinct().Sum(w => w.Length) + wordsB.Distinct().Sum(w => w.Length));
}
	public static void Main()
	{
    var res = IntersectionSize(
    	"Economie - Un oeil sur les medias"
    ,   "Un oeil sur les medias - Economie du mond"
    );
    Console.WriteLine(res);
}
}

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