D. Дождевая вода

#include <iostream>
#include <sstream>
#include <exception>
#include <cmath>
#include <unordered_set>
#include <vector>
#include <unordered_map>
#include <algorithm>
using namespace std;

void cv(vector <int> v) {
    for (int el: v) {
        cout << el << ' ';
    } cout << "\n";
}

int n;
vector <int> a;

int l(int R) {
    cout << "R: " << R <<"\n";
    if  (R == 0 || R == n - 1){
        return 0;
    }
    auto max_it = max_element(a.begin(), a.begin() +  R - 1);
    int mxi = R - (abs(distance(a.begin() + R, max_it)));
    cout << "mxi: " << mxi << "\n";
    cout << "dst: " << abs(distance(a.begin() + R, max_it)) << "\n";
    int s = 0;
    int h = a[mxi];
    cout << "h: " << h << "\n";
    for (int i = R - 1; i >= mxi; --i) {
        if (h < a[i]) {
            continue;
        }
        cout << "i: " << i << "\n";
        s += h - a[i];
    }
    cout << "s: " << s << "\n";
    cout << "\n";
    int add = l(mxi);
    return s + add;
}

int r(int L) {
    cout << "L: " << L << "\n";
    if (L == n - 1 || L == 0) {
        return 0;
    }
    auto max_it = max_element(a.begin() + L + 1, a.end());
    int mxi = L + abs(distance(a.begin() + L, max_it));
    cout << "mxi: " << mxi << "\n";
    cout << "dst: " << abs(distance(a.begin() + L, max_it)) << "\n";
    int s = 0;
    int h = a[mxi];
    cout << "h: " << h << "\n";
    for (int i = L + 1; i <= mxi; ++i) {
        if (h < a[i]) {
            continue;
        }
        cout << "i: " << i << "\n";
        s += h - a[i];
    }
    cout << "s: " << s << "\n";
    cout << "\n";
    int add = r(mxi);
    return s + add;
}
/*
10
7 0 4 2 5 0 6 4 0 5

16
1 2 4 0 0 5 4 2 6 8 2 3 4 5 5 3
*/
int main() {
     cin >> n;
    a.resize(n);
    for (int &el: a) cin >> el;
    auto max_it = max_element(a.begin(), a.end());
    int mxi = distance(a.begin(), max_it);
    int s = l(mxi) + r(mxi);
    cout << s << "\n";
}