#include <bits/stdc++.h>
#define fr first
#define sc second
#define pii pair<int, int>
#define pb push_back
#define szof(s) (int)s.size()
#define all(s) s.begin(), s.end()
#define fastInp ios_base::sync_with_stdio(0); cin.tie(0);
#define int long long
template<class T>void chmax(T &a, T b){if (a < b)a = b;}
template<class T>void chmin(T &a, T b){if (b < a)a = b;}
using namespace std;
const int MAXN = (int)2e5 + 5;
const int INF = 1e18;
int a[MAXN];
int arr[MAXN];
signed main() {
fastInp;
int n;
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> arr[i];
}
int ans = INF;
for (int k = 1; k <= n; k++) {
for (int j = 1; j <= n; j++) {
a[j] = arr[j];
}
int cur_ans = 0;
int l = k - 1;
int r = k + 1;
while (1) {
while (1 <= l && a[l] < a[l + 1]) {
l--;
}
while (r <= n && a[r - 1] > a[r]) {
r++;
}
if (l == 0 && r == n + 1) {
chmin(ans, cur_ans);
break;
}
if (l >= 1 && r <= n) {
int min_diff = min(a[l] - a[l + 1], a[r] - a[r - 1]);
cur_ans += min_diff + 1;
a[l + 1] += min_diff + 1;
a[r - 1] += min_diff + 1;
}
else if (l == 0) {
int diff = a[r] - a[r - 1];
cur_ans += diff + 1;
a[r - 1] += diff + 1;
}
else if (r == n + 1) {
int diff = a[l] - a[l + 1];
cur_ans += diff + 1;
a[l + 1] += diff + 1;
}
}
}
cout << ans << endl;
}
/*
8
12 2 34 85 4 91 29 85
*/
