#include <bits/stdc++.h>
const int maxn = 1e4 + 7;
using namespace std;
int n, h[maxn], l[maxn], r[maxn], sum;

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> h[i];
		l[i] = max(l[i - 1], h[i]);
	}
	for (int i = n; i > 0; i--)
		r[i] = max(r[i + 1] - h[i]);
	for (int i = 1; i <= n; i++) {
		sum += (min(l[i], r[i]) - h[i]);
	}
	cout << sum;
}

▁▁Orz▁▁

如有大佬回复，一定多多感谢