Initial data commit

Task/Diversity-prediction-theorem/C-sharp/diversity-prediction-theorem.cs

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+using System;
+using System.Linq;
+using System.Collections.Generic;
+
+public class MainClass {
+    static double Square(double x) => x * x;
+
+    static double AverageSquareDiff(double a, IEnumerable<double> predictions)
+        => predictions.Select(x => Square(x - a)).Average();
+
+    static void DiversityTheorem(double truth, IEnumerable<double> predictions)
+    {
+        var average = predictions.Average();
+        Console.WriteLine($@"average-error: {AverageSquareDiff(truth, predictions)}
+crowd-error: {Square(truth - average)}
+diversity: {AverageSquareDiff(average, predictions)}");
+    }
+	
+    public static void Main() {
+	DiversityTheorem(49, new []{48d,47,51});
+    	DiversityTheorem(49, new []{48d,47,51,42});
+    }
+}