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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <algorithm>
#include <cstdio>
#include <ctype.h>
#include <functional>
#include <iostream>
#include <cassert>
#include <cfloat>
#include <climits>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
#define int long long
using namespace std;

signed main() {
	int res, N;
	res = 0;
	cin >> N;
	vector<int> a(N);
	int b;
	for (int i = 0; i < N; i++) {
		cin >> b;
		a[b - 1] = i + 1;
	}
	
	set<int> st;
	st.insert(0);
	st.insert(N + 1);
	int x, y;
	for (int i = 0; i < N; i++) {
		y = *st.lower_bound(a[i]);
		x = *(--st.upper_bound(a[i]));
		//cerr << x << " "<<y<<endl;
		res += (i+1)*(a[i] - x)*(y - a[i]);
		st.insert(a[i]);
	}
	cout << res << endl;

	return 0;
}