static Dictionary<Double, Double> calc_distribution(List<double> v, int n){
            var result = new Dictionary<double, double>();
            double wmin = v[0], wmax = v[0];
            int wcount = 0;
            int wzero = 0;
            foreach (var p in v){
                if (p == -1) continue;
                if (p == 0) ++wzero;
                if (p < wmin) wmin = p;
                if (p > wmax) wmax = p;
                ++wcount;
            }
            double delta = (wmax-wmin)/n;

            List<double> c = new List<double>();
            c.AddRange(Enumerable.Repeat<double>(0,n));
            foreach (var p in v){
                if (p < 0) continue;
                int i = Math.Min((int)(p/delta),c.Count-1);
                ++c[i];
            }
            result.Add(0,(double)wzero/wcount);
            result.Add(delta, c[0] / wcount);
            for (int i=1; i<c.Count; ++i){
                c[i] += c[i-1];
                result.Add(delta * (i + 1), c[i] / wcount);
            }
            return result;
        }