using System;

public class Program
{
    static int SumPos(int[] a)
    {
        int r = 0;
        foreach (int x in a) if (x > 0) r += x;
        return r;
    }

    static int SumNeg(int[] a)
    {
        int r = 0;
        foreach (int x in a) if (x < 0) r += x;
        return r;
    }

    static int SumArr(int[] a) => SumPos(a) + SumNeg(a);

    static double AvgArr(int[] a) => a.Length == 0 ? double.NaN : (double)SumArr(a) / a.Length;

    static int SumEvenPos(int[] a)
    {
        int r = 0;
        for (int i = 0; i < a.Length; i += 2) r += a[i];
        return r;
    }

    static int SumOddPos(int[] a)
    {
        int r = 0;
        for (int i = 1; i < a.Length; i += 2) r += a[i];
        return r;
    }

    static int MaxIdx(int[] a)
    {
        if (a.Length == 0) return -1;
        int idx = 0, m = a[0];
        for (int i = 1; i < a.Length; i++)
            if (a[i] > m) { m = a[i]; idx = i; }
        return idx;
    }

    static int MinIdx(int[] a)
    {
        if (a.Length == 0) return -1;
        int idx = 0, m = a[0];
        for (int i = 1; i < a.Length; i++)
            if (a[i] < m) { m = a[i]; idx = i; }
        return idx;
    }

    static int ProductBetweenMinMax(int[] a)
    {
        int start = MinIdx(a), end = MaxIdx(a);
        if (start == -1 || end == -1) return -1;
        if (start > end) { int t = start; start = end; end = t; }
        if (end - start <= 1) return -1;
        int r = 1;
        for (int i = start + 1; i < end; i++) r *= a[i];
        return r;
    }

    public static void Main(string[] args)
    {
        Console.Write("input an arr length: ");
        int n = int.Parse(Console.ReadLine());
        int[] arr = new int[n];

        for (int i = 0; i < arr.Length; i++)
        {
            Console.Write("arr[{0}] = ", i);
            arr[i] = int.Parse(Console.ReadLine());
        }

        Console.WriteLine("sum of the array's elements is {0}", SumArr(arr));
        Console.WriteLine("avg value of the array is {0}", AvgArr(arr));
        Console.WriteLine("sum of positive array values is {0}, sum of negative array values is {1}", SumPos(arr), SumNeg(arr));
        Console.WriteLine("sum of elements on even positions is {0}, sum of elements on odd positions is {1}", SumEvenPos(arr), SumOddPos(arr));
        Console.WriteLine("index of max array element is {0}", MaxIdx(arr));
        Console.WriteLine("index of min array element is {0}", MinIdx(arr));
        Console.WriteLine("product of numbers between min and max is {0}", ProductBetweenMinMax(arr));
    }
}