class Program
    {
        static void Main(string[] args)
        {
            var values = new int[] {-10, 1, 2, 3, 4, -10, 2, 3, - 20, 1, 2, 3, 4, 5 };
            var s = MaxSubValue(values);

            Console.WriteLine($"begin {s.begin}; end: {s.end}; sum {s.sum}");
            Console.ReadLine();
        }

        public static Slice MaxSubValue(int[] values)
        {
            var previous = 0;
            var sum = 0;
            var begin = 0;
            var end = 0;

            for (var i = 0; i < values.Length; i++)
            {
                if (values[i] + sum > sum)
                {
                    sum += values[i];
                    end = i;
                }
                else
                {
                    begin = i + 1;
                    previous = sum;
                    sum = 0;
                }
            }

            return new Slice
            {
                begin = begin,
                end = end,
                sum = Math.Max(previous, sum)
            };
        }

        public struct Slice
        {
            public int begin;
            public int end;
            public int sum;
        }
    }