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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;
import java.util.TreeSet;

public class Main {

	public static void main(String[] args) {
		new Main().solve();
	}
	
	void solve(){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[]a=new int[n];
		for(int i=0;i<n;++i){
			a[i]=sc.nextInt();
		}
		TreeSet<Integer> seen=new TreeSet<>();
		seen.add(-1);
		seen.add(n);
		int[] w=new int[n];
		for(int i=0;i<n;++i){
			w[a[i]-1]=i;
		}
		long res=0;
		for(int i=0;i<n;++i){
			seen.add(w[i]);
			int prev=seen.headSet(w[i], false).last();
			int next=seen.tailSet(w[i], false).first();
			res+=(w[i]-prev)*(long)(next-w[i])*(i+1);
		}
		System.out.println(res);
	}
}