using System;

public class Program

{

    // this assumes that all the values in the series correspond to a week and the array is sorted according to that

    public static double[] ComputeTrendline(int[] timeSeries, bool computeOneFuturePoint) {

        int n = timeSeries.Length;

        double sumX = 0;

        double sumY = 0;

        double sumXY = 0;

        double sumXX = 0;

        for(int i=0; i<n; i++) {

            sumX += i;

            sumY += timeSeries[i];

            sumXY += i * timeSeries[i];

            sumXX += i * i;

        }

        double slope = (n * sumXY - sumX * sumY) / (n * sumXX - sumX * sumX);

        double intercept = (sumY - slope * sumX) / n;

        int m = computeOneFuturePoint ? n+1 : n;

        double[] trendline = new double[m];

        for(int j=0; j<m; j++) {

            trendline[j] = intercept + slope * j;

        }

        return trendline;

    }

    public static void Main()

    {

        int[] scores = {79, 75, 73, 81, 84, 88, 86};

        bool computeOneFuturePoint = false;

        double[] trendline = ComputeTrendline(scores, computeOneFuturePoint);

        Array.ForEach(trendline, Console.WriteLine);

    }

}