Problem:
Score : 400 points

Problem Statement

One day, Snuke was given a permutation of length N, a_1, a_2, ..., a_N, from his friend.

Find the following:

Constraints

1 ≦ N ≦ 200,000

(a_1, a_2, ..., a_N) is a permutation of (1, 2, ..., N).

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

Print the answer.

Note that the answer may not fit into a 32-bit integer.

Sample Input 1

3
2 1 3

Sample Output 1

9

Sample Input 2

4
1 3 2 4

Sample Output 2

19

Sample Input 3

8
5 4 8 1 2 6 7 3

Sample Output 3

85

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            List<int> A = Console.ReadLine().Split().Select(f => int.Parse(f)).ToList();
            int count = 0;
            List<int> sort = Enumerable.Range(0, N).ToList();
            int[] larr = Enumerable.Range(-1, N).ToArray();
            int[] rarr = Enumerable.Range(1, N).ToArray();
            sort.Sort((a, b) => A[b] - A[a]);
            for (int i = 0; i < N; i++)
            {
                var l = larr[sort[i]];
                var r = rarr[sort[i]];
                if (sort[i] != N-1)
                {
                    int lv = larr[sort[i] + 1];
                    for (int x = sort[i] + 1; x < N && lv == larr[x]; x++)
                    {
                        larr[x] = l;
                    }
                }
                if (sort[i] != 0)
                {
                    int rv = rarr[sort[i] - 1];
                    for (int x = sort[i] - 1; x >= 0 && rv == rarr[x]; x--)
                    {
                        rarr[x] = r;
                    }
                }
                count += A[sort[i]] * (sort[i] - l) * (r- sort[i]);
            }
            Console.WriteLine(count);
        }
    }
}