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 <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(){
    int N;
    cin >> N;
    vector<int> a(N);
    vector<pair<int,int> > ord(N);
    for(int i = 0; i < N; ++i){
        cin >> a[i];
        ord[i].first = a[i];
        ord[i].second = i;
    }
    sort(ord.begin(), ord.end());

    vector<int> len(N, 1);

    long long ans = 0;
    for(int i = N-1; i >= 0; --i){
        int cur = ord[i].second;
        int left = 0;
        int right = 0;
        if(cur > 0 && a[cur-1] > a[cur]){
            left = len[cur-1];
        }
        if(cur < N-1 && a[cur+1] > a[cur]){
            right = len[cur+1];
        }
        ans += (long long)(ord[i].first) * (left+1) * (right+1);
        len[cur - left] = left+right+1;
        a[cur -left] = ord[i].first;
        len[cur + right] = left+right+1;
        a[cur + right] = ord[i].first;
    }
    cout << ans << endl;
    return 0;
}