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: Time Limit Exceeded)

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());
            Dictionary<int,int> A = Console.ReadLine().Split().Select((f,i) => new Tuple<int,int>(int.Parse(f),i)).ToDictionary(f=>f.Item1,f=>f.Item2);
            
            long sum = 0;
            for (int i = 1; i <= n; i++)
            {
                int lef = 0;
                int rig = n-1;
                var lefB = A.Where(f => f.Key < i && f.Value < A[i]);
                if (lefB.Count() > 0)
                    lef = lefB.Max(f => f.Value)+1;
                var rigB = A.Where(f => f.Key < i && f.Value > A[i]);
                if (rigB.Count() > 0)
                    rig = rigB.Min(f => f.Value)-1;
                sum += i * (A[i] - lef + 1) * (rig - A[i] + 1);
            }
            Console.WriteLine(sum);
        }
    }
}