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: Runtime Error)

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;

// (づ°ω°)づﾐe★゜・。。・゜゜・。。・゜☆゜・。。・゜゜・。。・゜
public class Solver
{
    class SparseTable<T>
    {
        private const int MAX_LENGTH = 100000;
        private static int[] log = new int[MAX_LENGTH + 1];

        private readonly Comparison<T> comparison;
        private readonly int[,] table;
        private readonly T[] data;
        private readonly int length;
        private readonly int height;

        static SparseTable()
        {
            int c = 1;
            for (int i = 1; c <= MAX_LENGTH; i++)
                for (; c <= MAX_LENGTH && c < 1 << i; c++)
                    log[c] = i - 1;
        }

        public SparseTable(Comparison<T> comparison, T[] array)
        {
            this.comparison = comparison;
            data = array;
            length = array.Length;
            height = log[length] + 1;

            table = new int[length, height];
            for (int i = 0; i < length; i++)
                table[i, 0] = i;

            for (int i = 1; i < height; i++)
            {
                int bi = 1 << i;
                int pbi = 1 << i - 1;
                for (int j = 0; j + bi <= length; j++)
                {
                    int left = table[j, i - 1];
                    int right = table[j + pbi, i - 1];
                    if (comparison(data[left], data[right]) < 0)
                        table[j, i] = left;
                    else
                        table[j, i] = right;
                }
            }
        }

        public int Query(int l, int r)
        {
            int w = log[r - l + 1];
            int left = table[l, w];
            int right = table[r - (1 << w) + 1, w];
            if (comparison(data[left], data[right]) < 0)
                return left;
            return right;
        }
    }

    public void Solve()
    {
        int n = ReadInt();
        var a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = ReadInt();
        var table = new SparseTable<int>((x1, x2) => x1.CompareTo(x2), a);

        var stack = new Stack<Tuple<int, int>>();
        stack.Push(Tuple.Create(0, n - 1));
        long ans = 0;
        while (stack.Count > 0)
        {
            int l = stack.Peek().Item1;
            int r = stack.Pop().Item2;
            if (l > r)
                continue;
            int x = table.Query(l, r);
            ans += 1L * a[x] * (x - l + 1) * (r - x + 1);
            stack.Push(Tuple.Create(l, x - 1));
            stack.Push(Tuple.Create(x + 1, r));
        }

        Write(ans);
    }

    #region Main

    protected static TextReader reader;
    protected static TextWriter writer;
    static void Main()
    {
#if DEBUG
        reader = new StreamReader("..\\..\\input.txt");
        //reader = new StreamReader(Console.OpenStandardInput());
        writer = Console.Out;
        //writer = new StreamWriter("..\\..\\output.txt");
#else
        reader = new StreamReader(Console.OpenStandardInput());
        writer = new StreamWriter(Console.OpenStandardOutput());
        //reader = new StreamReader("input.txt");
        //writer = new StreamWriter("output.txt");
#endif
        try
        {
            new Solver().Solve();
            //var thread = new Thread(new Solver().Solve, 1024 * 1024 * 128);
            //thread.Start();
            //thread.Join();
        }
        catch (Exception ex)
        {
#if DEBUG
            Console.WriteLine(ex);
#else
            throw;
#endif
        }
        reader.Close();
        writer.Close();
    }

    #endregion

    #region Read / Write
    private static Queue<string> currentLineTokens = new Queue<string>();
    private static string[] ReadAndSplitLine() { return reader.ReadLine().Split(new[] { ' ', '\t', }, StringSplitOptions.RemoveEmptyEntries); }
    public static string ReadToken() { while (currentLineTokens.Count == 0)currentLineTokens = new Queue<string>(ReadAndSplitLine()); return currentLineTokens.Dequeue(); }
    public static int ReadInt() { return int.Parse(ReadToken()); }
    public static long ReadLong() { return long.Parse(ReadToken()); }
    public static double ReadDouble() { return double.Parse(ReadToken(), CultureInfo.InvariantCulture); }
    public static int[] ReadIntArray() { return ReadAndSplitLine().Select(int.Parse).ToArray(); }
    public static long[] ReadLongArray() { return ReadAndSplitLine().Select(long.Parse).ToArray(); }
    public static double[] ReadDoubleArray() { return ReadAndSplitLine().Select(s => double.Parse(s, CultureInfo.InvariantCulture)).ToArray(); }
    public static int[][] ReadIntMatrix(int numberOfRows) { int[][] matrix = new int[numberOfRows][]; for (int i = 0; i < numberOfRows; i++)matrix[i] = ReadIntArray(); return matrix; }
    public static int[][] ReadAndTransposeIntMatrix(int numberOfRows)
    {
        int[][] matrix = ReadIntMatrix(numberOfRows); int[][] ret = new int[matrix[0].Length][];
        for (int i = 0; i < ret.Length; i++) { ret[i] = new int[numberOfRows]; for (int j = 0; j < numberOfRows; j++)ret[i][j] = matrix[j][i]; } return ret;
    }
    public static string[] ReadLines(int quantity) { string[] lines = new string[quantity]; for (int i = 0; i < quantity; i++)lines[i] = reader.ReadLine().Trim(); return lines; }
    public static void WriteArray<T>(IEnumerable<T> array) { writer.WriteLine(string.Join(" ", array)); }
    public static void Write(params object[] array) { WriteArray(array); }
    public static void WriteLines<T>(IEnumerable<T> array) { foreach (var a in array)writer.WriteLine(a); }
    private class SDictionary<TKey, TValue> : Dictionary<TKey, TValue>
    {
        public new TValue this[TKey key]
        {
            get { return ContainsKey(key) ? base[key] : default(TValue); }
            set { base[key] = value; }
        }
    }
    private static T[] Init<T>(int size) where T : new() { var ret = new T[size]; for (int i = 0; i < size; i++)ret[i] = new T(); return ret; }
    #endregion
}