Revise paste 3119ed6f8eedc

#include <iostream>
#include <vector>
#include <map>
#include <stack>
//#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9 + 7;
int main()
{
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;
    
    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
    
    vector<int> left(n, -1), right(n, n);
    
    stack<int> st;
    for(int i = 0; i < n; i++) {
        while(!st.empty() and v[st.top()] > v[i]) {
            st.pop();
        }
        if(!st.empty()) {
            left[i] = st.top();
        }
        st.push(i);
    }
    
    stack<int> st2;
    for(int i = n - 1; i >= 0; i--) {
        while(!st2.empty() and v[st2.top()] > v[i]) {
            st2.pop();
        }
        if(!st2.empty()) {
            right[i] = st2.top();
        }
        
        st2.push(i);
    }
    
    ll total_subarrays = (ll)n * (ll) (n + 1) / 2LL;
    total_subarrays %= MOD;
    
    ll bad_subarrays = 0;
    for(int i = 0; i < n; i++) {
        ll L = i - left[i], R = right[i] - i;
        
        bad_subarrays += (L * R) % MOD;
        bad_subarrays %= MOD;
    }
    
    cout << (total_subarrays - bad_subarrays + MOD) % MOD << endl;
        
    return 0;
}