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 <bits/stdc++.h>

using namespace std;

#define pb push_back
#define mp make_pair
#define forn(i, n) for (int i = 0; i < (int)(n); ++i)
typedef long long LL;
typedef pair<int, int> PII;

int n;
int a[200005], le[200005], ri[200005];

int main() {
    scanf("%d", &n);
    forn(i, n) scanf("%d", a + i);
    forn(i, n) {
        le[i] = i;
        while (le[i] > 0 && a[le[i] - 1] >= a[i]) {
            le[i] = le[le[i] - 1];
        }
    }
    for (int i = n - 1; i >= 0; --i) {
        ri[i] = i;
        while (ri[i] < n - 1 && a[ri[i] + 1] > a[i]) {
            ri[i] = ri[ri[i] + 1];
        }
    }
    LL ans = 0;
    forn(i, n) {
        ans += (LL)a[i] * (ri[i] - i + 1) * (i - le[i] + 1);
    }
    cout << ans << endl;
    return 0;
}