#include<bits/stdc++.h>
using namespace std;

void solve() {
    vector <int> h = {5, 0, 2, 1, 4, 0, 1, 0, 3};
    int n = h.size(), ans = 0;
    vector<int> max_l(n), max_r(n);
    if (n == 0) {
    	return;
	}
    max_l[0] = h[0];
    for (int i = 1; i < n; ++i) {
        max_l[i] = max(max_l[i - 1], h[i]);
    }
    max_r[n - 1] = h[n - 1];
    for (int i = n - 2; i >= 0; --i) {
        max_r[i] = max(max_r[i + 1], h[i]);
    }
    for (int i = 0; i < n; ++i) {
        ans += min(max_l[i], max_r[i]) - h[i];
    }
	cout << ans << endl;
    return;
}

int main() {
	solve();
	return 0;
}